Change branch references from 'main' to 'master'

Author: djpbarry

.github/workflows/links.yml

@@ -2,9 +2,9 @@ name: Check links
 
 on:
   push:
-    branches: [main]
+    branches: [master]
   pull_request:
-    branches: [main]
+    branches: [master]
   schedule:
     - cron: '0 6 * * 1'   # Weekly on Mondays at 06:00 UTC
   workflow_dispatch:      # Lets you run it manually from the Actions tab