Create PRs as drafts to prompt maintainers to trigger PR checks

PR checks won't be triggered on PRs created by Actions workflows.
Therefore mark PRs created by workflows as draft to prompt maintainers
to take the PR out of draft, thereby triggering PR checks.

.github/update-release-branch.py

@@ -93,7 +93,9 @@ def open_pr(repo, all_commits, short_main_sha, branch_name):
   title = 'Merge ' + MAIN_BRANCH + ' into ' + LATEST_RELEASE_BRANCH
 
   # Create the pull request
-  pr = repo.create_pull(title=title, body='\n'.join(body), head=branch_name, base=LATEST_RELEASE_BRANCH)
+  # PR checks won't be triggered on PRs created by Actions. Therefore mark the PR as draft so that
+  # a maintainer can take the PR out of draft, thereby triggering the PR checks.
+  pr = repo.create_pull(title=title, body='\n'.join(body), head=branch_name, base=LATEST_RELEASE_BRANCH, draft=True)
   print('Created PR #' + str(pr.number))
 
   # Assign the conductor

.github/workflows/post-release-mergeback.yml

@@ -106,19 +106,14 @@ jobs:
           git commit -m "Update changelog and version after $VERSION"
           npm version patch
 
-          # when running this workflow on a PR, this is just a test.
-          # so put into draft mode.
-          if [ "$GITHUB_EVENT_NAME" == "pull_request" ]; then
-            DRAFT="--draft"
-          else
-            DRAFT=""
-          fi
-
           git push origin "$NEW_BRANCH"
+
+          # PR checks won't be triggered on PRs created by Actions. Therefore mark the PR as draft
+          # so that a maintainer can take the PR out of draft, thereby triggering the PR checks.
           gh pr create \
             --head "$NEW_BRANCH" \
             --base "$BASE_BRANCH" \
             --title "$PR_TITLE" \
             --label "Update dependencies" \
             --body "$PR_BODY" \
-            ${DRAFT:+"$DRAFT"} # no quotes around $DRAFT. gh will error out if there is an empty ""
+            --draft

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

@@ -27,7 +27,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install PyGithub==1.51 requests
+        pip install PyGithub==1.55 requests
 
     - name: Update git config
       run: |