removed sisl.plot from the code base

[zerothi]

• Closes #x
• Added tests for new/changed functions?
• Ran isort . and black . [24.2.0] at top-level
• Documentation for functionality in docs/
• Changes documented in CHANGELOG.md

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.77%. Comparing base (f8a90fe) to head (7da0684).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #753      +/-   ##
==========================================
- Coverage   86.78%   86.77%   -0.01%     
==========================================
  Files         412      410       -2     
  Lines       51967    51785     -182     
==========================================
- Hits        45101    44939     -162     
+ Misses       6866     6846      -20     

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