DOC: fix no autosummary for numerical index api pages
For some reason the 'class_without_autosummary' template is not working for the newly added numeric index classes.

I asked in the PR https://github.com/pandas-dev/pandas/pull/17611 to combine them, but now as a test splitting them again (all other cases where it does work is only one class, but if this works seems a bug in sphinx)

Don't merge yet.