gha: update master branch to main

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

Author: thaJeztah

.github/workflows/build.yml

@@ -17,7 +17,7 @@ on:
   workflow_dispatch:
   push:
     branches:
-      - 'master'
+      - 'main'
     tags:
       - 'v*'
   pull_request: