Make show_versions not to reload modules (GH13684)
closes #13684 

## [Current coverage](https://codecov.io/gh/pydata/pandas/pull/14126?src=pr) is 85.27% (diff: 0.00%)

> Merging [#14126](https://codecov.io/gh/pydata/pandas/pull/14126?src=pr) into [master](https://codecov.io/gh/pydata/pandas/branch/master?src=pr) will decrease coverage by **<.01%**

``` diff
@@             master     #14126   diff @@
==========================================
  Files           139        139          
  Lines         50529      50531     +2   
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
  Hits          43089      43089          
- Misses         7440       7442     +2   
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last update [47a8e71...74bfb21](https://codecov.io/gh/pydata/pandas/compare/47a8e713430707afcfe76e7ca995902628d4bccf...74bfb2178eb5da19d6e77e9f78ade9b721cf120d?src=pr)
 lgtm.
