Update Python dependencies before running trigger_workflow script. (#3200)

Author: jonsimantov

.github/workflows/update-cpp-sdk-on-release.yml

@@ -71,4 +71,5 @@ jobs:
 
       - name: Trigger firebase-cpp-sdk update
         run: |
+          pip install -r scripts/gha/requirements.txt
           python scripts/gha/trigger_workflow.py -t ${{ steps.generate-token.outputs.token }} -w update-dependencies.yml -p updateAndroid 1 -p updateiOS 0 -p comment "[Triggered]($GITHUB_SERVER_URL/$GITHUB_REPOSITORY/actions/runs/$GITHUB_RUN_ID) by [firebase-android-sdk $(date '+%b %d') release]($GITHUB_SERVER_URL/$GITHUB_REPOSITORY/commit/${{ github.sha }})." -s 10 -A