use built-in concurrency configuration for duplicate workflows

[zacharyburnett]

In regards to cancelling duplicate workflows, this PR replaces the cancel_workflows.yml workflow with the built-in concurrency block.

This is:

1. faster
2. reduces the amount of workflows in the Actions queue, and
3. reduces our dependence on third-party workflow actions

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (e5aca99) 54.17% compared to head (d634bf5) 54.17%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #89   +/-   ##
=======================================
  Coverage   54.17%   54.17%           
=======================================
  Files          25       25           
  Lines        3057     3057           
=======================================
  Hits         1656     1656           
  Misses       1401     1401           

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.