ci: set dependabot blocking to high severity (chaynHQ#1014)

Author: annarhughes

.github/workflows/dependabot-pr-review.yml

@@ -19,4 +19,4 @@ jobs:
         uses: actions/dependency-review-action@v4
         with:
           # fails when moderate vulnerabilities are deteched
-          fail-on-severity: moderate
+          fail-on-severity: high