github/workflows: fix branch name

.github/workflows/main.yml

@@ -3,10 +3,10 @@ name: build
 'on':
   push:
     branches:
-      - main
+      - master
   pull_request:
     branches:
-      - main
+      - master
   # Allows you to run this workflow manually from the Actions tab
   workflow_dispatch:
 jobs: