Drop a python2 backport deps (enum34, subprocess32, configparser)

[jbylund]

Fixes #2992

Description

Removes a few backported libs that were necessary to support python 2.7 (and maybe 3.5-).

Testing

Ran tox, but worried that this is exactly the type of stuff that's likely to have limited coverage.

[raubitsj]

Great!
We have been planning on doing this, thanks for doing this.
I wasnt sure if configparser was an exact backport of what is in python3.6+

Also you can drop tying also since the package doesnt support python3.5 any more

[jbylund]

I wasnt sure if configparser was an exact backport of what is in python3.6+

Based on the readme, it appears that wand has been using the stdlib version of configparser since it wasn't doing from backports ....

[codecov]

Codecov Report

Merging #3004 (3d519da) into master (4b640ec) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #3004      +/-   ##
==========================================
+ Coverage   79.03%   79.05%   +0.01%     
==========================================
  Files         210      210              
  Lines       27640    27636       -4     
==========================================
+ Hits        21846    21847       +1     
+ Misses       5794     5789       -5     

Flag	Coverage Δ
functest	57.05% <100.00%> (+0.05%)	⬆️
unittest	68.84% <100.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
wandb/sdk/internal/internal_api.py	83.69% <100.00%> (+0.09%)	⬆️
wandb/sdk/internal/meta.py	90.68% <100.00%> (+3.56%)	⬆️
wandb/filesync/step_prepare.py	92.85% <0.00%> (-1.43%)	⬇️
wandb/sdk/internal/stats.py	67.22% <0.00%> (-0.56%)	⬇️
wandb/sdk/lib/git.py	76.35% <0.00%> (ø)

[dmitryduev]

👍🏻 Will merge once the CI is green.