RLS: switch master from 0.18.2 to 0.19.0
xref #13562 

prob pandas/doc/release.rst as well.
 `release.rst` did not yet include anything about 0.18.2 (we always only add right before the release I think)
 ## [Current coverage](https://codecov.io/gh/pydata/pandas/pull/13586?src=pr) is **84.31%**

> Merging [#13586](https://codecov.io/gh/pydata/pandas/pull/13586?src=pr) into [master](https://codecov.io/gh/pydata/pandas/branch/master?src=pr) will not change coverage

``` diff
@@             master     #13586   diff @@
==========================================
  Files           138        138          
  Lines         51155      51155          
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
  Hits          43130      43130          
  Misses         8025       8025          
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last updated by [2655dae...1494280](https://codecov.io/gh/pydata/pandas/compare/2655daef1b7346feabd00d4d40910a80386d0812...1494280e7d4fee52627b7c9a4833292a1dca0259?src=pr)
 Merging, so other PRs can be rebased on to this with the new whatsnew file
