ci: explicitly set workflow_dispatch as empty mapping

Author: qectorlab

.github/workflows/build.yml

@@ -14,7 +14,7 @@ on:
     branches: [main, master]
     tags: ["v*", "ci-*", "test-*"]
   pull_request:
-  workflow_dispatch:
+  workflow_dispatch: {}
 
 permissions:
   contents: read