DOC: Removed duplicate doc line
This line of documentation is already included in the parent shared docs. So the line appears twice. See the screenshot below from [the Dataframe.aggregate page](https://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.aggregate.html). My patch cleans that up.

![screenshot from 2019-01-07 17-00-12](https://user-images.githubusercontent.com/9993/50803035-ca04fa00-129d-11e9-8078-a0a3d9a55400.png)

Looking at the dev docs I think there are actually a few other issues with this one. Do you mind taking a look?

http://pandas-docs.github.io/pandas-docs-travis/api/generated/pandas.DataFrame.aggregate.html?highlight=aggregate#pandas.DataFrame.aggregate
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24668?src=pr&el=h1) Report
> Merging [#24668](https://codecov.io/gh/pandas-dev/pandas/pull/24668?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/be406f316d7aa27d565894059fc609329f055972?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/24668/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24668?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #24668   +/-   ##
=======================================
  Coverage   92.37%   92.37%           
=======================================
  Files         166      166           
  Lines       52315    52315           
=======================================
  Hits        48327    48327           
  Misses       3988     3988
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.79% <ø> (ø)` | :arrow_up: |
| #single | `43.06% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24668?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/24668/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `96.92% <ø> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24668?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/24668?src=pr&el=footer). Last update [be406f3...d4c941b](https://codecov.io/gh/pandas-dev/pandas/pull/24668?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/24668?src=pr&el=h1) Report
> Merging [#24668](https://codecov.io/gh/pandas-dev/pandas/pull/24668?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/be406f316d7aa27d565894059fc609329f055972?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/24668/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24668?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #24668   +/-   ##
=======================================
  Coverage   92.37%   92.37%           
=======================================
  Files         166      166           
  Lines       52315    52315           
=======================================
  Hits        48327    48327           
  Misses       3988     3988
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.79% <ø> (ø)` | :arrow_up: |
| #single | `43.06% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24668?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/24668/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `96.92% <ø> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24668?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/24668?src=pr&el=footer). Last update [be406f3...d4c941b](https://codecov.io/gh/pandas-dev/pandas/pull/24668?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @palewire do you mind running `./scripts/validate_docstrings.py pandas.DataFrame.aggregate` and copy the full output here in a comment? That will make it easier to review.

I'm not sure your fix is correct, as the latest version is different from your screenshot and the link you referred to. Seems like there is a problem with the sections, and those notes are now rendered in the returns section.

You may also want to run `./doc/make.py html --single=pandas.DataFrame.aggregate` to see how your changes will look like. @WillAyd @palewire @datapythonista  

I've tried to fix the issues. The PR is here #24948. Please let me know if anything is amiss. close this in favor of #24948, a more comprehensive fix.