ci: remove pull_request trigger from Release Drafter workflow

The pull_request trigger caused Release Drafter to fail with:
  'Validation Failed: field target_commitish invalid'

This happens because on PR events, release-drafter uses refs/pull/N/merge
as target_commitish when updating the draft release, which the GitHub
Releases API rejects as an invalid ref.

The pull_request trigger is only needed for autolabeler functionality,
which is currently commented out in the workflow. Removing it fixes the
recurring failure while preserving all desired behavior (draft updates
happen on push to main).

Author: Ritchie

.github/workflows/release-drafter.yml

@@ -5,10 +5,11 @@ on:
     # branches to consider in the event; optional, defaults to all
     branches:
       - main
-  # pull_request event is required only for autolabeler
-  pull_request:
-    # Only following types are handled by the action, but one can default to all as well
-    types: [opened, reopened, synchronize]
+  # pull_request event is only needed for autolabeler (currently disabled)
+  # Removing it prevents the "invalid target_commitish" error when Release Drafter
+  # tries to use refs/pull/N/merge as a release target, which GitHub rejects.
+  # pull_request:
+  #   types: [opened, reopened, synchronize]
   # pull_request_target event is required for autolabeler to support PRs from forks
   # pull_request_target:
   #   types: [opened, reopened, synchronize]
@@ -31,7 +32,7 @@ jobs:
       #  run: |
       #    echo "GHE_HOST=${GITHUB_SERVER_URL##https:\/\/}" >> $GITHUB_ENV
 
-      # Drafts your next Release notes as Pull Requests are merged into "master"
+      # Drafts your next Release notes as Pull Requests are merged into "main"
       - uses: release-drafter/release-drafter@v7
         # (Optional) specify config name to use, relative to .github/. Default: release-drafter.yml
         # with: