refactor: move the source_ref grammar out of sync

The site imported two parsing functions from profile_sync, so every change to the comparison tool redeployed an unchanged site. The grammar now lives in sourceref.py.

.github/workflows/deploy-site.yml

@@ -26,7 +26,6 @@ on:
       - "scripts/packpaths.py"
       - "scripts/packreadme.py"
       - "scripts/packresolve.py"
-      - "scripts/profile_sync.py"
       - "scripts/provenance_report.py"
       - "scripts/refresh_data_dirs.py"
       - "scripts/region.py"
@@ -38,6 +37,7 @@ on:
       - "scripts/sitesources.py"
       - "scripts/sitewrite.py"
       - "scripts/slots.py"
+      - "scripts/sourceref.py"
       - "scripts/split_pack.py"
       - "scripts/truth.py"
       - "scripts/upstream.py"