drop Python 3.7 support, remove its dependencies

[ariebovenberg]

Description

Before merge

• tox runs successfully
• Docs updated

Before release (if applicable)

• Version updated in pyproject.toml
• Version updated in pre-commit hook example
• Version updated in changelog
• Branch merged
• Tag created and pushed
• Published

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (62d0477) 100.00% compared to head (973e992) 100.00%.

❗ Current head 973e992 differs from pull request most recent head 6fd30e2. Consider uploading reports for the commit 6fd30e2 to get more accurate results

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #175   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            6         6           
  Lines          508       508           
  Branches       107       107           
=========================================
  Hits           508       508           

Files Changed	Coverage Δ
src/slotscheck/cli.py	100.00% <ø> (ø)
src/slotscheck/__init__.py	100.00% <100.00%> (ø)
src/slotscheck/checks.py	100.00% <100.00%> (ø)
src/slotscheck/common.py	100.00% <100.00%> (ø)

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