chore: set coverage calculations to manual trigger only (#5080)

Co-authored-by: Mikolaj Umanski <mumanski@microsoft.com>

.github/workflows/check-coverage.yml

@@ -1,9 +1,6 @@
 name: "Test coverage"
 on:
-  push:
-    branches: ["master"]
-  pull_request:
-    branches: ["master"]
+  workflow_dispatch:
 
 permissions:
   id-token: write