Installing missing depedency

Author: xrmx

.github/workflows/prepare-release-branch.yml

@@ -60,7 +60,9 @@ jobs:
         run: .github/scripts/update-version.sh $STABLE_VERSION $UNSTABLE_VERSION
 
       - name: Update contrib sha to match a branch with the same name of this
-        run: python3 scripts/update_sha.py -b $RELEASE_BRANCH_NAME
+        run: |
+          pip install ruamel.yaml
+          python3 scripts/update_sha.py -b $RELEASE_BRANCH_NAME
 
       - name: Update the change log with the approximate release date
         run: |