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.
lgtm. merge when ready. Nope, it is not fixing the problem ... (not sure what causes it: for some reason the 'class_without_autosummary' template is not working for the numerical index classes, although it does work fine for eg CategoricalIndex which already used this long before) @jorisvandenbossche is it related to https://github.com/pandas-dev/pandas/blob/e0fe5cc60b1dc0d777223bba64b8abfc0e0e02ab/doc/sphinxext/numpydoc/numpydoc.py#L45?

After the release, I hope to devote some time to getting us working with numpydoc proper and the most recent version of sphinx. Ah yes .. of course. Though I wrote that hack myself I think .. (so the template is actually not working)

> After the release, I hope to devote some time to getting us working with numpydoc proper and the most recent version of sphinx.

Yes, that is also already a long time on my to do list, but never got to it. We have in the mean time quite some hacks like this added, but it would be nice to get it working with upstream (on sklearn they did a similar effort recently and pushed some changes upstream). Happy to help on it!
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17642?src=pr&el=h1) Report
> Merging [#17642](https://codecov.io/gh/pandas-dev/pandas/pull/17642?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/4004367fb815645bb7f5bbb518eee62cbd476e3a?src=pr&el=desc) will **decrease** coverage by `0.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17642/graphs/tree.svg?height=150&width=650&token=eZ4WkYLtcO&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/17642?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17642      +/-   ##
==========================================
- Coverage   91.22%    91.2%   -0.02%     
==========================================
  Files         163      163              
  Lines       49655    49655              
==========================================
- Hits        45297    45288       -9     
- Misses       4358     4367       +9
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.99% <ø> (ø)` | :arrow_up: |
| #single | `40.17% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17642?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17642?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17642?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.77% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17642?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17642?src=pr&el=footer). Last update [4004367...cded21b](https://codecov.io/gh/pandas-dev/pandas/pull/17642?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17642?src=pr&el=h1) Report
> Merging [#17642](https://codecov.io/gh/pandas-dev/pandas/pull/17642?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/4004367fb815645bb7f5bbb518eee62cbd476e3a?src=pr&el=desc) will **decrease** coverage by `0.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17642/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/17642?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17642      +/-   ##
==========================================
- Coverage   91.22%    91.2%   -0.02%     
==========================================
  Files         163      163              
  Lines       49655    49655              
==========================================
- Hits        45297    45288       -9     
- Misses       4358     4367       +9
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.99% <ø> (ø)` | :arrow_up: |
| #single | `40.17% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17642?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17642?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17642?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.77% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17642?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17642?src=pr&el=footer). Last update [4004367...cded21b](https://codecov.io/gh/pandas-dev/pandas/pull/17642?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 This seems to be working now, so lets add some more hack and merge this. Thanks Tom for reminding me of the hack :-)