Do not run rss-to-bluesky job on schedule on forks

Within the blueskyfeedbot action there is a job rss-to-bluesky which will try to create bluesky posts for gtn news posts.
This _should_ not run on forks and as there are no secrets in forks it also _can_ not run in forks (and it fails).
As this action is triggered daily via cron, it is pretty annoying having a fork with daily failing runs triggering daily emails to the dev.
This commit allows scheduled runs only on the galaxyproject/training-material repository and not on forks. However, for forks it is still possible to trigger the action manually, e.g. for testing.

Author: mittler-works

.github/workflows/blueskyfeedbot.yml

@@ -10,6 +10,7 @@ concurrency:
   group: feedbot
 jobs:
   rss-to-bluesky:
+    if: (github.event_name == 'schedule' && github.repository == 'galaxyproject/training-material') || (github.event_name != 'schedule')
     runs-on: ubuntu-latest
     steps:
       - name: Generate cache key