REQUESTS_CA_BUNDLE and CURL_CA_BUNDLE environment variables get ignored when in a venv

<!-- Summary. -->
Requests supports the REQUESTS_CA_BUNDLE and CURL_CA_BUNDLE environment variables to override the certificate 

## Expected Result
<!-- What you expected. -->
Here's what's happening outside of the venv
```
REQUESTS_CA_BUNDLE=/etc/ssl/certs/ca-certificates.crt python3
Python 3.11.8 (main, Feb 08 2024, 08:03:16) [GCC] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import certifi
>>> certifi.where()
'/etc/ssl/certs/ca-certificates.crt'
```
## Actual Result
<!-- What happened instead. -->
Inside the venv:
```
fried@linux:/tmp> python3 -m venv .venv
fried@linux:/tmp> source .venv/bin/activate
(.venv) fried@linux:/tmp> pip install requests
Collecting requests
  Downloading requests-2.31.0-py3-none-any.whl.metadata (4.6 kB)
Collecting charset-normalizer<4,>=2 (from requests)
  Downloading charset_normalizer-3.3.2-cp311-cp311-manylinux_2_17_x86_64.manylinux2014_x86_64.whl.metadata (33 kB)
Collecting idna<4,>=2.5 (from requests)
  Downloading idna-3.6-py3-none-any.whl.metadata (9.9 kB)
Collecting urllib3<3,>=1.21.1 (from requests)
  Downloading urllib3-2.2.1-py3-none-any.whl.metadata (6.4 kB)
Collecting certifi>=2017.4.17 (from requests)
  Downloading certifi-2024.2.2-py3-none-any.whl.metadata (2.2 kB)
Downloading requests-2.31.0-py3-none-any.whl (62 kB)
   ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 62.6/62.6 kB 3.4 MB/s eta 0:00:00
Downloading certifi-2024.2.2-py3-none-any.whl (163 kB)
   ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 163.8/163.8 kB 5.3 MB/s eta 0:00:00
Downloading charset_normalizer-3.3.2-cp311-cp311-manylinux_2_17_x86_64.manylinux2014_x86_64.whl (140 kB)
   ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 140.3/140.3 kB 10.9 MB/s eta 0:00:00
Downloading idna-3.6-py3-none-any.whl (61 kB)
   ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 61.6/61.6 kB 5.7 MB/s eta 0:00:00
Downloading urllib3-2.2.1-py3-none-any.whl (121 kB)
   ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 121.1/121.1 kB 10.1 MB/s eta 0:00:00
Installing collected packages: urllib3, idna, charset-normalizer, certifi, requests
Successfully installed certifi-2024.2.2 charset-normalizer-3.3.2 idna-3.6 requests-2.31.0 urllib3-2.2.1

(.venv) fried@linux:/tmp> REQUESTS_CA_BUNDLE=/etc/ssl/certs/ca-certificates.crt python3
Python 3.11.8 (main, Feb 08 2024, 08:03:16) [GCC] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import certifi
>>> certifi.where()
'/tmp/.venv/lib64/python3.11/site-packages/certifi/cacert.pem'
>>> 
```

## Reproduction Steps

```bash
$ python3 -m venv .venv
$ source .venv/bin/activate
$ REQUESTS_CA_BUNDLE=/etc/ssl/certs/ca-certificates.crt python
>>> import certifi
>>> certifi.where()
```

## System Information

    $ python -m requests.help

```json
{
  "chardet": {
    "version": null
  },
  "charset_normalizer": {
    "version": "3.3.2"
  },
  "cryptography": {
    "version": ""
  },
  "idna": {
    "version": "3.6"
  },
  "implementation": {
    "name": "CPython",
    "version": "3.11.8"
  },
  "platform": {
    "release": "6.7.7-1-default",
    "system": "Linux"
  },
  "pyOpenSSL": {
    "openssl_version": "",
    "version": null
  },
  "requests": {
    "version": "2.31.0"
  },
  "system_ssl": {
    "version": "30100040"
  },
  "urllib3": {
    "version": "2.2.1"
  },
  "using_charset_normalizer": true,
  "using_pyopenssl": false
}
```

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please provide some basic information about your system (Python version,
operating system, &c). -->


A few things:

1. Requests isn't in use in your examples; you're using `certifi`. 
2. My guess, is that outside of the venv you have `certifi` from your package manager, and every Linux distro replaces `certifi` with something else
3. `certifi` (a separate project) does not support either environment variable, Requests does.
4. Requests will continue to honor what you set, except in cases like #3829 
5. Lastly, I think this is effectively a duplicate of #6565 

Duplicate of #6565