Merge pull request #4652 from rubyforgood/pull-request-force-push

Update PULL_REQUEST_TEMPLATE.md

.github/PULL_REQUEST_TEMPLATE.md

@@ -8,6 +8,7 @@
 - I have added tests that prove my fix is effective or that my feature works,
 - New and existing unit tests pass locally with my changes ("bundle exec rake"),
 - Title include "WIP" if work is in progress.
+- I acknowledge that I will *not* force push my branch once reviews have started.
 
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