Pin actions/github-script to commit SHA in first-time-contributor workflow (#6730)

Signed-off-by: harshitghagre <harshitghagre183@gmail.com>

Author: harshitghagre

.github/workflows/first-time-contributor.yaml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Welcome first-time contributor
-        uses: actions/github-script@v7
+        uses: actions/github-script@f28e40c7f34bde8b3046d885e986cb6290c5673b # v7
         with:
           script: |
             const owner = context.repo.owner;