.github/workflows/ci-conda.yml: On pull_request, only run 1 macOS job

Author: Matthias Koeppe

.github/workflows/ci-conda.yml

@@ -24,11 +24,18 @@ jobs:
       fail-fast: ${{ github.event_name == 'pull_request' }}
       max-parallel: ${{ github.event_name == 'pull_request' && 2 || 6 }}
       matrix:
-        os: [ubuntu-latest, macos-latest]
+        os: >-
+          ${{ github.event_name == 'pull_request'
+                && fromJson('["ubuntu-latest"]')
+                || fromJson('["ubuntu-latest", "macos-latest"]') }}
         python: ['3.9', '3.10', '3.11']
         # Optional environment is disabled for now as its not yet working
         # environment: [environment, environment-optional]
         conda-env: [environment]
+        include: >-
+          ${{ github.event_name == 'pull_request'
+                && fromJson('[{"os": "macos-latest", "python": "3.11", "conda-env": "environment"}]')
+                || fromJson('[]') }}
 
     steps:
       - uses: actions/checkout@v4