Return to fail-fast: true

[skip ci]

Author: apdavison

.github/workflows/core-test.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ${{ matrix.os }}
 
     strategy:
-      fail-fast: false   # temporary for extending matrix, should normally be true
+      fail-fast: true
       matrix:
         os: ["ubuntu-latest", "windows-latest"]
         # "macos-latest",