DOC: the source link of CategoricalIndex's methods are wrong.
#### Location of the documentation

- [ ] https://pandas.pydata.org/docs/dev/reference/api/pandas.CategoricalIndex.add_categories.html
- [ ] https://pandas.pydata.org/docs/dev/reference/api/pandas.CategoricalIndex.rename_categories.html
- [ ] https://pandas.pydata.org/docs/dev/reference/api/pandas.CategoricalIndex.reorder_categories.html
- [ ] https://pandas.pydata.org/docs/dev/reference/api/pandas.CategoricalIndex.remove_categories.html
- [ ] https://pandas.pydata.org/docs/dev/reference/api/pandas.CategoricalIndex.remove_unused_categories.html
- [ ] https://pandas.pydata.org/docs/dev/reference/api/pandas.CategoricalIndex.set_categories.html
- [ ] https://pandas.pydata.org/docs/dev/reference/api/pandas.CategoricalIndex.as_ordered.html
- [ ] https://pandas.pydata.org/docs/dev/reference/api/pandas.CategoricalIndex.as_unordered.html
#### Documentation problem

For example, in pandas.CategoricalIndex.add_categories, the source link jumps to the following source.This link is wrong.
As far as I've observed, the above methods all jump to the same wrong link.
https://github.com/pandas-dev/pandas/blob/40b2aa56c3779d0178069e8182dcc3bcdc102e57/pandas/core/accessor.py#L98-L99

The source link should jump to the following location.
https://github.com/pandas-dev/pandas/blob/40daf00721f358105f744e8aad7b0c524d1c417b/pandas/core/arrays/categorical.py#L943

#### Suggested fix for documentation
Correct the source link.