Backport PR #25134 on branch 0.24.x (DOC: restore toctree maxdepth)
Backport PR #25134: DOC: restore toctree maxdepth
Doc build passed and looks OK. # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25664?src=pr&el=h1) Report
> Merging [#25664](https://codecov.io/gh/pandas-dev/pandas/pull/25664?src=pr&el=desc) into [0.24.x](https://codecov.io/gh/pandas-dev/pandas/commit/0fa95802328aaa8466534308bd648e770bcf93d6?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25664/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25664?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           0.24.x   #25664   +/-   ##
=======================================
  Coverage   92.39%   92.39%           
=======================================
  Files         166      166           
  Lines       52424    52424           
=======================================
  Hits        48437    48437           
  Misses       3987     3987
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.83% <ø> (ø)` | :arrow_up: |
| #single | `42.9% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25664?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/25664?src=pr&el=footer). Last update [0fa9580...429d6d4](https://codecov.io/gh/pandas-dev/pandas/pull/25664?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/25664?src=pr&el=h1) Report
> Merging [#25664](https://codecov.io/gh/pandas-dev/pandas/pull/25664?src=pr&el=desc) into [0.24.x](https://codecov.io/gh/pandas-dev/pandas/commit/0fa95802328aaa8466534308bd648e770bcf93d6?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25664/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25664?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           0.24.x   #25664   +/-   ##
=======================================
  Coverage   92.39%   92.39%           
=======================================
  Files         166      166           
  Lines       52424    52424           
=======================================
  Hits        48437    48437           
  Misses       3987     3987
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.83% <ø> (ø)` | :arrow_up: |
| #single | `42.9% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25664?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/25664?src=pr&el=footer). Last update [0fa9580...429d6d4](https://codecov.io/gh/pandas-dev/pandas/pull/25664?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
