gallery workflow - update branch name

Author: wsmelton

.github/workflows/gallery.yml

@@ -2,10 +2,10 @@ name: Publish Gallery
 on:
   push:
     branches:
-      - master
+      - main
   pull_request:
     branches:
-      - master
+      - main
 permissions:
   id-token: write
   actions: write