Set branch for github actions

Author: arnavbhate

.github/workflows/nextjs.yml

@@ -7,7 +7,7 @@ name: Deploy Next.js site to Pages
 on:
   # Runs on pushes targeting the default branch
   push:
-    branches: [$default-branch]
+    branches: ["main"]
 
   # Allows you to run this workflow manually from the Actions tab
   workflow_dispatch: