Remove yard rake tasks

[ekohl]

This drops all yard related rake tasks, since we don't list yard in our
gem dependencies anyway. Even if you do add it, it fails to generate.

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (9a4e935) 84.74% compared to head (2a04dea) 84.74%.

❗ Current head 2a04dea differs from pull request most recent head 2b6bfa9. Consider uploading reports for the commit 2b6bfa9 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #96   +/-   ##
=======================================
  Coverage   84.74%   84.74%           
=======================================
  Files           1        1           
  Lines         295      295           
=======================================
  Hits          250      250           
  Misses         45       45           

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 in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.