fix: more cython3 optional fixes

[bdraco]

there were a few more places that were missing optional which is now strictly enforced with cython3

[codecov]

Codecov Report

Patch coverage: 88.88% and project coverage change: -0.25% ⚠️

Comparison is base (7826897) 82.73% compared to head (7b0be3f) 82.48%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #219      +/-   ##
==========================================
- Coverage   82.73%   82.48%   -0.25%     
==========================================
  Files          27       27              
  Lines        3220     3220              
  Branches      668      668              
==========================================
- Hits         2664     2656       -8     
- Misses        342      346       +4     
- Partials      214      218       +4     

Files Changed	Coverage Δ
src/dbus_fast/__version__.py	0.00% <0.00%> (ø)
src/dbus_fast/aio/message_reader.py	90.90% <ø> (ø)
src/dbus_fast/glib/message_bus.py	80.32% <ø> (-2.05%)	⬇️
src/dbus_fast/aio/message_bus.py	85.57% <100.00%> (ø)
src/dbus_fast/auth.py	87.93% <100.00%> (ø)
src/dbus_fast/introspection.py	84.92% <100.00%> (ø)
src/dbus_fast/service.py	88.65% <100.00%> (ø)

... and 1 file with indirect coverage changes

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