MAINT: remove shebang from test modules
 - [x] closes #15131 
## [Current coverage](https://codecov.io/gh/pandas-dev/pandas/pull/15134?src=pr) is 85.53% (diff: 100%)
> Merging [#15134](https://codecov.io/gh/pandas-dev/pandas/pull/15134?src=pr) into [master](https://codecov.io/gh/pandas-dev/pandas/branch/master?src=pr) will decrease coverage by **<.01%**

```diff
@@             master     #15134   diff @@
==========================================
  Files           145        145          
  Lines         51288      51288          
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
- Hits          43872      43871     -1   
- Misses         7416       7417     +1   
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last update [1f82f18...3b6c960](https://codecov.io/gh/pandas-dev/pandas/compare/1f82f18933e42f0c9695b551cfce98cd1632f841...3b6c960f0f93eee29381ba6e7ef9e3f39851288a?src=pr) thanks!