CLN: Removed / filled stub read_csv tests
Title is self-explanatory.

xref #4782

## [Current coverage](https://codecov.io/gh/pydata/pandas/pull/13864?src=pr) is 85.25% (diff: 100%)

> Merging [#13864](https://codecov.io/gh/pydata/pandas/pull/13864?src=pr) into [master](https://codecov.io/gh/pydata/pandas/branch/master?src=pr) will increase coverage by **<.01%**

``` diff
@@             master     #13864   diff @@
==========================================
  Files           140        140          
  Lines         50455      50455          
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
+ Hits          43014      43015     +1   
+ Misses         7441       7440     -1   
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last update [59f2557...4da1ba4](https://codecov.io/gh/pydata/pandas/compare/59f25575f42e19f066dc3cd2245983071e2d7813...4da1ba4511ce3e9f4d1b6a9464e26bd186181ce9?src=pr)
 thanks @gfyoung 
