MAINT validate_params for plot_tree (#25882)

### Describe the bug


The March 20, 2023 commit  (MAINT validate_params for plot_tree (#25882) ) of the file:
**scikit-learn/sklearn/tree/_export.py**
introduced the parameter validation of the **plot_tree** function that does not seem to agree with the documentation in the docstring or website.  The parameter validation seems to omit the bool option described in the help.  This option was previously permissible.  Has it been removed as a valid option or is the parameter validation missing this option?


```
  @validate_params(
      {
  ...
          "class_names": _**[list, None]**_,
  ...
      }
  )

class_names : list of str or **_bool_**, default=None
    Names of each of the target classes in ascending numerical order.
    Only relevant for classification and not supported for multi-output.
    If ``True``, shows a symbolic representation of the class name.
```

### Steps/Code to Reproduce

```python
from sklearn import datasets
from sklearn.model_selection import train_test_split
from sklearn.tree import DecisionTreeClassifier
from sklearn.tree import plot_tree
import matplotlib.pyplot as plt

SEED = 42

data = datasets.load_wine()
X = data.data
y = data.target

X_train, X_test, y_train, y_test = train_test_split(X, y, random_state=SEED)

dt = DecisionTreeClassifier(max_depth=4, random_state=SEED)
dt.fit(X_train, y_train)

features = data.feature_names
classes = data.target_names.tolist()


plot_tree(dt, feature_names=features, class_names=classes)
plt.show()

# Works in 1.2.2, error in 1.3.0
plot_tree(dt, feature_names=features, class_names=True)
plt.show()
```

### Expected Results

No error is thrown.

### Actual Results

```
 Traceback (most recent call last):

  File ~\Anaconda3\envs\py311\Lib\site-packages\spyder_kernels\py3compat.py:356 in compat_exec
    exec(code, globals, locals)

  File c:\temp\decisiontree.py:26
    plot_tree(dt, feature_names=features, class_names=True)

  File ~\Anaconda3\envs\py311\Lib\site-packages\sklearn\utils\_param_validation.py:201 in wrapper
    validate_parameter_constraints(

  File ~\Anaconda3\envs\py311\Lib\site-packages\sklearn\utils\_param_validation.py:95 in validate_parameter_constraints
    raise InvalidParameterError(

InvalidParameterError: The 'class_names' parameter of plot_tree must be an instance of 'list' or None. Got True instead.
```

### Versions

```shell
import sklearn; sklearn.show_versions()

System:
    python: 3.9.17 (main, Jul  5 2023, 21:22:06) [MSC v.1916 64 bit (AMD64)]
executable: C:\Users\lance.endres\Anaconda3\python.exe
   machine: Windows-10-10.0.19044-SP0

Python dependencies:
      sklearn: 1.2.2
          pip: 23.2.1
   setuptools: 68.0.0
        numpy: 1.21.5
        scipy: 1.10.1
       Cython: 0.29.32
       pandas: 1.5.3
   matplotlib: 3.7.1
       joblib: 1.2.0
threadpoolctl: 2.2.0

Built with OpenMP: True

threadpoolctl info:
       filepath: C:\Users\lance.endres\Anaconda3\Library\bin\mkl_rt.1.dll
         prefix: mkl_rt
       user_api: blas
   internal_api: mkl
        version: 2021.4-Product
    num_threads: 6
threading_layer: intel

       filepath: C:\Users\lance.endres\Anaconda3\vcomp140.dll
         prefix: vcomp
       user_api: openmp
   internal_api: openmp
        version: None
    num_threads: 12

       filepath: C:\Users\lance.endres\Anaconda3\Library\bin\libiomp5md.dll
         prefix: libiomp
       user_api: openmp
   internal_api: openmp
        version: None
    num_threads: 12
```

COMMENT:
already fixed in https://github.com/scikit-learn/scikit-learn/pull/26903

Labels: Bug, Needs Triage