Only report DAG sync when DAG files have changed

[AetherUnbound]

Description

PR #871 recently got reported to our Slack channel when it was deployed, even though it doesn't have any change to operational DAG code. This appears to be because we were only searching for /dags/ in the path string, and that also includes changes to DAG tests only. This PR changes the DAG sync messaging so it only reports after changes to actual operational DAG code are deployed.

Testing Instructions

Merge and see!

Checklist

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[sarayourfriend]

LGTM

[krysal]

LGTM