Dev - add ruff check for unused imports F401 (SYN-10235)

[vEpiphyte]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 95.83333% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 97.73%. Comparing base (f3f571f) to head (85990ac).

Files with missing lines	Patch %	Lines
synapse/tools/autodoc.py	0.00%	1 Missing ⚠️
synapse/tools/backup.py	0.00%	1 Missing ⚠️
synapse/tools/genpkg.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4731      +/-   ##
==========================================
- Coverage   97.73%   97.73%   -0.01%     
==========================================
  Files         298      298              
  Lines       62352    62329      -23     
==========================================
- Hits        60941    60916      -25     
- Misses       1411     1413       +2     

Flag	Coverage Δ
linux	97.65% <95.83%> (-0.02%)	⬇️
linux_replay	93.41% <95.83%> (+0.01%)	⬆️

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[vEpiphyte]

@MichaelSquires I'm not certain why the patch coverage is failing on this PR; since this is net negative lines of code.