fix(ci): Update GitHub GHC matrix

 * Only build macOS on ghc96
 * Remove ghc92 from all builds

Author: sgillespie

.github/workflows/haskell.yml

@@ -19,11 +19,11 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        compiler-nix-name: [ghc810, ghc92, ghc96]
+        compiler-nix-name: [ghc810, ghc96]
         include:
           # We want a single job, because macOS runners are scarce.
           - os: macos-latest
-            compiler-nix-name: ghc810
+            compiler-nix-name: ghc96
 
     steps:
       - name: Checkout code