Exclude macos/GHC8.8.4 build

Author: robdockins

.github/workflows/ci.yml

@@ -64,6 +64,8 @@ jobs:
         exclude:
           - os: windows-latest
             ghc: "8.8.4"
+          - os: macos-latest
+            ghc: "8.8.4"
     outputs:
       cabal-test-suites-json: ${{ steps.cabal-test-suites.outputs.targets-json }}
     steps: