Drop support for python 3.7

[eapolinario]

TL;DR

Please replace this text with a description of what this PR accomplishes.

Type

• Bug Fix
• Feature
• Plugin

Are all requirements met?

• Code completed
• Smoke tested
• Unit tests added
• Code documentation added
• Any pending items have an associated Issue

Complete description

How did you fix the bug, make the feature etc. Link to any design docs etc

Tracking Issue

https://github.com/flyteorg/flyte/issues/

Follow-up issue

NA
OR
https://github.com/flyteorg/flyte/issues/

[wild-endeavor]

punch it

[codecov]

Codecov Report

Merging #1521 (6c6ad75) into master (4ea2ee4) will decrease coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1521      +/-   ##
==========================================
- Coverage   69.28%   69.26%   -0.03%     
==========================================
  Files         315      315              
  Lines       28845    28844       -1     
  Branches     2741     2741              
==========================================
- Hits        19986    19978       -8     
- Misses       8341     8349       +8     
+ Partials      518      517       -1     

Impacted Files	Coverage Δ
flytekit/configuration/default_images.py	28.57% <ø> (+1.29%)	⬆️
setup.py	0.00% <ø> (ø)
...s/flytekit/unit/configuration/test_image_config.py	100.00% <ø> (ø)
flytekit/core/data_persistence.py	32.01% <0.00%> (-3.51%)	⬇️
flytekit/clients/auth/authenticator.py	48.30% <0.00%> (ø)

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.