Remove comment

Author: c-warren

community/how-to-contribute/pull-request-conventions.mdx

@@ -31,7 +31,6 @@ docs: Update getting started guide
 
 ### PR Title Guidelines
 
-<!-- Source: https://github.com/cadence-workflow/cadence/blob/master/CONTRIBUTING.md#L253-L265 -->
 Follow the [Chris Beams guide](http://chris.beams.io/posts/git-commit/) to writing git commit messages. All PR titles should:
 
 - Start with UPPER case