Fix badges + bump min python

[esoteric-ephemera]

• Fix badges to only point to test passing on main
• Bump min python consistent with emmet-core / numpy version support

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.44%. Comparing base (4747310) to head (f27a6b2).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1049   +/-   ##
=======================================
  Coverage   76.44%   76.44%           
=======================================
  Files          50       50           
  Lines        2793     2793           
=======================================
  Hits         2135     2135           
  Misses        658      658           

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