ci: Fix triggers (#882)

Currently on a branch a workflow got triggered 2x one time on push and one time as its a PR
Now it only gets triggered on PR and on push onto main

Reviewed-on: https://gitea.com/gitea/runner/pulls/882
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Nicolas <bircni@icloud.com>
Co-committed-by: Nicolas <bircni@icloud.com>

.gitea/workflows/test.yml

@@ -1,7 +1,9 @@
 name: checks
 on:
-  - push
-  - pull_request
+  push:
+    branches:
+      - main
+  pull_request:
 
 jobs:
   lint: