Alias Raspbian to Debian

[cottsay]

Debian is the upstream source for Debian packages.

OS_RASPBIAN was added to rospkg in ros-infrastructure/rospkg#244 and was released in 1.4.0.

Note that there aren't any detectors behind OS_RASPBIAN right now. It will be a breaking change for rospkg to switch detecting Raspbian as debian and start detecting as raspbian instead, and this change prepares for that eventuality.

[codecov-commenter]

Codecov Report

Merging #867 (97e5052) into master (9342649) will decrease coverage by 0.01%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master     #867      +/-   ##
==========================================
- Coverage   75.03%   75.02%   -0.02%     
==========================================
  Files          42       42              
  Lines        3333     3339       +6     
==========================================
+ Hits         2501     2505       +4     
- Misses        832      834       +2     

Impacted Files	Coverage Δ
src/rosdep2/platforms/debian.py	78.73% <66.66%> (-0.44%)	⬇️

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[nuclearsandwich]

Thanks for remembering to update the minimum rospkg version.