`Index.droplevel()` should not be permitted

[Dr-Irv]

Describe the bug
Index.droplevel() is not supported.

So if a user knows that they have a MultiIndex (e.g., df.index.droplevel(), they should be forced to do a cast.

To Reproduce

>>> import pandas as pd
>>> df = pd.DataFrame({"x":[1,2]})
>>> df
   x
0  1
1  2
>>> df.columns.droplevel([0])
Traceback (most recent call last):
  File "<python-input-3>", line 1, in <module>
    df.columns.droplevel([0])
    ~~~~~~~~~~~~~~~~~~~~^^^^^
  File "C:\Condadirs\envs\base313\Lib\site-packages\pandas\core\indexes\base.py", line 2301, in droplevel
    return self._drop_level_numbers(levnums)
           ~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^
  File "C:\Condadirs\envs\base313\Lib\site-packages\pandas\core\indexes\base.py", line 2312, in _drop_level_numbers
    raise ValueError(
    ...<2 lines>...
    )
ValueError: Cannot remove 1 levels from an index with 1 levels: at least one level must be left.

So it doesn't work at runtime

Please complete the following information:

• OS: Windows 11
• OS Version 2H25
• python version 3.13
• version of type checker pyright 1.1.408 - it allows the above
• version of installed pandas-stubs - dev version

Additional context

We could not fix this because it forces a cast if you do something like this. But I think this is helpful to users to make them acknowledge that the corresponding index is a MultiIndex