Update CI, no on: pull_request by default

Author: sorki

.github/workflows/ci.dhall.frozen

@@ -1,6 +1,6 @@
 let haskellCi =
       https://raw.githubusercontent.com/sorki/github-actions-dhall/main/haskell-ci.dhall
-        sha256:5d7058a7684fd5315467b562853bd1c4a43da691c09293d3715ee739dfa26e08
+        sha256:a39801f73d93c6e0f91942755ef8ae4c50947e9a9b180b6724957229470f7b8d
 
 let defSteps = haskellCi.defaultCabalSteps
 

.github/workflows/ci.yaml

@@ -59,7 +59,6 @@ jobs:
         - "macos-latest"
 name: Haskell CI
 'on':
-  pull_request: {}
   push: {}
   schedule:
   - cron: "4 20 10 * *"