fix: fix modularity inconsistency by using get_igraph_from_adjacency for now.

[flying-sheep]

• Closes Inconsistency in graphs used by sc.tl.leiden and sc.metrics.modularity leads to modularity mismatch #4099
• Tests included or not required because:

• Release notes not necessary because:

[codecov]

Codecov Report

❌ Patch coverage is 83.33333% with 3 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (main@6af627e). Learn more about missing BASE report.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/scanpy/neighbors/__init__.py	0.00%	1 Missing ⚠️
src/scanpy/tools/_paga.py	0.00%	1 Missing ⚠️
src/scanpy/tools/_utils.py	85.71%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4112   +/-   ##
=======================================
  Coverage        ?   79.60%           
=======================================
  Files           ?      119           
  Lines           ?    12777           
  Branches        ?        0           
=======================================
  Hits            ?    10171           
  Misses          ?     2606           
  Partials        ?        0           

Flag	Coverage Δ
hatch-test.low-vers	78.88% <83.33%> (?)
hatch-test.pre	79.47% <83.33%> (?)

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Files with missing lines	Coverage Δ
src/scanpy/_utils/__init__.py	75.28% <100.00%> (ø)
src/scanpy/metrics/_metrics.py	97.14% <100.00%> (ø)
src/scanpy/plotting/_tools/paga.py	64.26% <100.00%> (ø)
src/scanpy/tools/_draw_graph.py	69.01% <100.00%> (ø)
src/scanpy/neighbors/__init__.py	82.04% <0.00%> (ø)
src/scanpy/tools/_paga.py	32.05% <0.00%> (ø)
src/scanpy/tools/_utils.py	86.76% <85.71%> (ø)