Run tests against Python 3.10

[cottsay]

Also drop PR branch wildcard to align with other ROS infrastructure CI workflows.

[codecov-commenter]

Codecov Report

Merging #883 (027908a) into master (b2ee64f) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #883      +/-   ##
==========================================
+ Coverage   74.82%   74.83%   +0.01%     
==========================================
  Files          44       44              
  Lines        3360     3362       +2     
==========================================
+ Hits         2514     2516       +2     
  Misses        846      846              

Impacted Files	Coverage Δ
src/rosdep2/meta.py	100.00% <0.00%> (ø)
src/rosdep2/sources_list.py	84.45% <0.00%> (+0.04%)	⬆️

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