ci: Fix GitHub workflow trigger specifying main instead of $default-branch

Author: jcfr

.github/workflows/build-website.yml

@@ -2,10 +2,10 @@ name: Deploy Jekyll site to Pages
 on:
   push:
     branches:
-      - $default-branch
+      - main
   pull_request:
     branches:
-      - $default-branch
+      - main
 
   # Allows you to run this workflow manually from the Actions tab
   workflow_dispatch: