Remove generated files from VCS

[amantoux]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.19%. Comparing base (7f965d0) to head (abdfd26).
Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #410      +/-   ##
==========================================
+ Coverage   87.91%   88.19%   +0.28%     
==========================================
  Files          62       62              
  Lines       10332    10575     +243     
==========================================
+ Hits         9083     9327     +244     
+ Misses       1249     1248       -1     

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[amantoux]

Canceling beacause files are generated by running flutter pub get from the fleather directory and will therefore not be generated when building or getting dependencies for any app implementing Fleather. This would cause some extra burden for implementors