Wrong way of checking if CustomModule is a subclass of torch.nn.Module 

### 🐛 Describe the bug

When I build my custom module and try to add it to a sequential text processing, with "[torchtext.transforms.Sequential](https://pytorch.org/text/stable/transforms.html#torchtext.transforms.Sequential)" It raises an error even though I'm doing the sub classing correctly.

This is a fragment of the error stack trace:
![image](https://github.com/pytorch/pytorch/assets/147768729/a5e62c5e-7cc8-40b4-aa3d-73bdfdd14da2)

When I go directly to the code to see what happens I find that the method used for checking if the provided module is a subclass of torch.nn.Module I find this:
![image](https://github.com/pytorch/pytorch/assets/147768729/a9939b8c-9270-4c81-90ee-e25470f3d92e)

This is a mistake because the function for doing the subclassing check is 'issubclass' instead of 'isinstance'. I changed the code and it worked as needed, so please check this bug out. 



### Versions

Collecting environment information...
PyTorch version: 2.1.0+cu121
Is debug build: False
CUDA used to build PyTorch: 12.1
ROCM used to build PyTorch: N/A

OS: Manjaro Linux (x86_64)
GCC version: (GCC) 13.2.1 20230801
Clang version: 16.0.6
CMake version: version 3.27.5
Libc version: glibc-2.38

Python version: 3.11.5 (main, Sep  2 2023, 14:16:33) [GCC 13.2.1 20230801] (64-bit runtime)
Python platform: Linux-6.1.53-1-MANJARO-x86_64-with-glibc2.38
Is CUDA available: True
CUDA runtime version: Could not collect
CUDA_MODULE_LOADING set to: LAZY
GPU models and configuration: GPU 0: NVIDIA GeForce GTX 1050 Ti
Nvidia driver version: 535.104.05
cuDNN version: Could not collect
HIP runtime version: N/A
MIOpen runtime version: N/A
Is XNNPACK available: True

CPU:
Architecture:                       x86_64
CPU op-mode(s):                     32-bit, 64-bit
Address sizes:                      43 bits physical, 48 bits virtual
Byte Order:                         Little Endian
CPU(s):                             12
On-line CPU(s) list:                0-11
Vendor ID:                          AuthenticAMD
Model name:                         AMD Ryzen 5 3600X 6-Core Processor
CPU family:                         23
Model:                              113
Thread(s) per core:                 2
Core(s) per socket:                 6
Socket(s):                          1
Stepping:                           0
Frequency boost:                    enabled
CPU(s) scaling MHz:                 70%
CPU max MHz:                        4408,5928
CPU min MHz:                        2200,0000
BogoMIPS:                           7603,86
Flags:                              fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl nonstop_tsc cpuid extd_apicid aperfmperf rapl pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt tce topoext perfctr_core perfctr_nb bpext perfctr_llc mwaitx cpb cat_l3 cdp_l3 hw_pstate ssbd mba ibpb stibp vmmcall fsgsbase bmi1 avx2 smep bmi2 cqm rdt_a rdseed adx smap clflushopt clwb sha_ni xsaveopt xsavec xgetbv1 cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local clzero irperf xsaveerptr rdpru wbnoinvd arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold avic v_vmsave_vmload vgif v_spec_ctrl umip rdpid overflow_recov succor smca sev sev_es
Virtualization:                     AMD-V
L1d cache:                          192 KiB (6 instances)
L1i cache:                          192 KiB (6 instances)
L2 cache:                           3 MiB (6 instances)
L3 cache:                           32 MiB (2 instances)
NUMA node(s):                       1
NUMA node0 CPU(s):                  0-11
Vulnerability Gather data sampling: Not affected
Vulnerability Itlb multihit:        Not affected
Vulnerability L1tf:                 Not affected
Vulnerability Mds:                  Not affected
Vulnerability Meltdown:             Not affected
Vulnerability Mmio stale data:      Not affected
Vulnerability Retbleed:             Mitigation; untrained return thunk; SMT enabled with STIBP protection
Vulnerability Spec rstack overflow: Mitigation; safe RET
Vulnerability Spec store bypass:    Mitigation; Speculative Store Bypass disabled via prctl
Vulnerability Spectre v1:           Mitigation; usercopy/swapgs barriers and __user pointer sanitization
Vulnerability Spectre v2:           Mitigation; Retpolines, IBPB conditional, STIBP always-on, RSB filling, PBRSB-eIBRS Not affected
Vulnerability Srbds:                Not affected
Vulnerability Tsx async abort:      Not affected

Versions of relevant libraries:
[pip3] numpy==1.26.1
[pip3] pytorch-lightning==2.1.0
[pip3] torch==2.1.0
[pip3] torchaudio==2.1.0
[pip3] torchdata==0.7.0
[pip3] torchmetrics==1.2.0
[pip3] torchtext==0.16.0
[pip3] torchvision==0.16.0
[pip3] triton==2.1.0
[conda] Could not collect