Fix CI (#816)

Not longer run CI on windows as dependencies are not ready yet.

Author: hhugo

.github/workflows/workflow.yml

@@ -3,6 +3,8 @@ name: Main workflow
 on:
   pull_request:
   push:
+    branches:
+      - master
   schedule:
     # Prime the caches every Monday
     - cron: 0 1 * * MON
@@ -15,7 +17,6 @@ jobs:
         os:
           - macos-latest
           - ubuntu-latest
-          - windows-latest
         ocaml-compiler:
           - "4.14"
           - "5.2"