Update R-CMD-check.yaml

Author: NRaillard

.github/workflows/R-CMD-check.yaml

@@ -4,7 +4,7 @@ on:
   push:
     branches: [main, master]
   pull_request:
-    branches: [main, master]
+    branches: []
   schedule:
     - cron: "27 3 * * 1"