DOC: Fix Numpy Docstring errors in pandas.api.extensions.ExtensionArray
Related to: https://github.com/pandas-dev/pandas/issues/58539

Fixes the following docstring checks:
```
        -i "pandas.api.extensions.ExtensionArray.duplicated RT03,SA01" \
        -i "pandas.api.extensions.ExtensionArray.fillna SA01" \
        -i "pandas.api.extensions.ExtensionArray.insert PR07,RT03,SA01" \
        -i "pandas.api.extensions.ExtensionArray.isin PR07,RT03,SA01" \
        -i "pandas.api.extensions.ExtensionArray.tolist RT03,SA01" \
        -i "pandas.api.extensions.ExtensionArray.unique RT03,SA01" \
        -i "pandas.api.extensions.ExtensionArray.view SA01" \
```
Thanks @abhinav-thimma 