DOC Minor what's new fix for v0.24
I think there is a word missing in the first sentence of the 0.24 what's new. Maybe it's just me but I was expecting some word after "See :ref:`install.dropping-27` for more.".

cc @TomAugspurger 
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24933?src=pr&el=h1) Report
> Merging [#24933](https://codecov.io/gh/pandas-dev/pandas/pull/24933?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/83eb2428ceb6257042173582f3f436c2c887aa69?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/24933/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24933?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #24933   +/-   ##
=======================================
  Coverage   92.38%   92.38%           
=======================================
  Files         166      166           
  Lines       52388    52388           
=======================================
  Hits        48397    48397           
  Misses       3991     3991
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.8% <ø> (ø)` | :arrow_up: |
| #single | `42.89% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24933?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/24933?src=pr&el=footer). Last update [83eb242...cba8e3e](https://codecov.io/gh/pandas-dev/pandas/pull/24933?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/24933?src=pr&el=h1) Report
> Merging [#24933](https://codecov.io/gh/pandas-dev/pandas/pull/24933?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/83eb2428ceb6257042173582f3f436c2c887aa69?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/24933/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24933?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #24933   +/-   ##
=======================================
  Coverage   92.38%   92.38%           
=======================================
  Files         166      166           
  Lines       52388    52388           
=======================================
  Hits        48397    48397           
  Misses       3991     3991
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.8% <ø> (ø)` | :arrow_up: |
| #single | `42.89% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24933?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/24933?src=pr&el=footer). Last update [83eb242...cba8e3e](https://codecov.io/gh/pandas-dev/pandas/pull/24933?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @rth : Thanks for the PR!  Could go either way IMO, but let's see what others think... did the merge bot not pick this up? I believe we have the milestone setup correctly. @TomAugspurger ? We didn't branch yet. And I only labeled after merging. Will do this one manually Has been backported