rationalize CI

Author: CarloLucibello

.github/workflows/ci.yml

@@ -22,10 +22,15 @@ jobs:
           - 'nightly'
         os:
           - ubuntu-latest
-          - macOS-latest
-          - windows-latest
         arch:
           - x64
+        include:
+          - os: windows-latest
+            version: '1'
+            arch: x64
+          - os: macOS-latest
+            version: '1'
+            arch: x64
     steps:
       - uses: actions/checkout@v2
       - uses: julia-actions/setup-julia@v1