Consistently "opinionated"

Co-authored-by: Matt Graham <[email protected]>

CONTRIBUTING.md

@@ -15,7 +15,7 @@ to be reviewed by a member or associate member of ARC.
 We will probably be slow to approve new tool suggestions (since we'll probably
 want to discuss them first) but don't let that put you off creating an issue!
 
-Any opinion changes should be approved by at least two reviewers who are
+Any opinionated changes should be approved by at least two reviewers who are
 members or associate members of ARC. Pull-request authors are trusted to add two
 reviewers to anything that they think might be opinionated. If a reviewer adds
 a second reviewer, please wait for both to approve before merging.