Do not run score cards on forks of flutter/flutter. (#97603)

As a general rule all the .github workflows enabled for flutter/flutter
should not run on forks.

Bug: https://github.com/flutter/flutter/issues/97599

.github/workflows/scorecards-analysis.yml

@@ -14,6 +14,7 @@ jobs:
   analysis:
     name: Scorecards analysis
     runs-on: ubuntu-latest
+    if: ${{ github.repository == 'flutter/flutter' }}
     permissions:
       # Needed to upload the results to code-scanning dashboard.
       security-events: write