Update SARIF upload to use proper branch (#82)

Author: mandreko-bitwarden

.github/workflows/scan.yml

@@ -48,6 +48,8 @@ jobs:
         uses: github/codeql-action/upload-sarif@17a820bf2e43b47be2c72b39cc905417bc1ab6d0 # v3.28.6
         with:
           sarif_file: cx_result.sarif
+          sha: ${{ contains(github.event_name, 'pull_request') && github.event.pull_request.head.sha || github.sha }}
+          ref: ${{ contains(github.event_name, 'pull_request') && format('refs/pull/{0}/head', github.event.pull_request.number) || github.ref }}
 
   quality:
     name: Quality scan