Bug: approvals not dismissed for merge commit with diff

[algae-elbaum]

This was a one time occurrence with no clear cause. The PR and commit involved are private and have been shared in DMs with @BakerNet

The scenario was:

1. PR opened with multiple (4) required review groups
2. After a comment and some changes, all required approvals were granted
3. Branch had a merge conflict with master, and the resulting merge commit included a diff in one of the PR's files
   i. The particular file was owned by one (1) review group, and this is probably not relevant, but in case it is, I (the PR author) am a member and maintainer of that review group.
4. Merge commit pushed, codeowners-plus bot rechecks PR

Expected: codeowners-plus bot dismisses reviews from owners of the file with the merge conflict diff

Actual: codeowners-plus bot comments "Codeowners reviews satisfied" and PR remains approved and clear to merge