fix: corrects Variant documentation

[Mocramis]

Variant documentation does not match the class signature since the fork from dbus-python.

It troubled me while reading the doc, so here is the (very small) fix.

[codecov]

Codecov Report

Base: 82.38% // Head: 82.31% // Decreases project coverage by -0.07% ⚠️

Coverage data is based on head (fbaa5e9) compared to base (6387f82).
Patch coverage: 0.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #197      +/-   ##
==========================================
- Coverage   82.38%   82.31%   -0.07%     
==========================================
  Files          27       27              
  Lines        3167     3167              
  Branches      654      654              
==========================================
- Hits         2609     2607       -2     
  Misses        343      343              
- Partials      215      217       +2     

Impacted Files	Coverage Δ
src/dbus_fast/__version__.py	0.00% <0.00%> (ø)
src/dbus_fast/signature.py	62.28% <ø> (ø)
src/dbus_fast/message_bus.py	71.48% <0.00%> (-0.37%)	⬇️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[Mocramis]

Removed three lines of comments so coverage reduced :/ not sure how to fix that.

[bdraco]

Thanks @Mocramis