Fix Python docstrings

[mdboom]

This just fixes the docstring formatting on dataclasses so they show up correctly in the generated docs. (No content changes, just moving things around...)

[codecov-io]

Codecov Report

Merging #493 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #493      +/-   ##
============================================
- Coverage     76.54%   76.53%   -0.02%     
  Complexity      331      331              
============================================
  Files            96       96              
  Lines          5603     5599       -4     
  Branches        650      650              
============================================
- Hits           4289     4285       -4     
  Misses          832      832              
  Partials        482      482

Impacted Files	Coverage Δ	Complexity Δ
...va/mozilla/telemetry/glean/config/Configuration.kt	94.73% <0%> (-0.92%)	8% <0%> (ø)

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