Update SonarSource/sonarqube-scan-action action to v6

Author: renovate[bot]

.github/workflows/flutter.yml

@@ -48,6 +48,6 @@ jobs:
           name: failures
           path: "**/failures/"
 
-      - uses: SonarSource/sonarqube-scan-action@1a6d90ebcb0e6a6b1d87e37ba693fe453195ae25 # v5.3.1
+      - uses: SonarSource/sonarqube-scan-action@fd88b7d7ccbaefd23d8f36f73b59db7a3d246602 # v6.0.0
         env:
           SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}