CI: disable Windows until cabal-install-3.10 is available

See haskell/actions#202 (comment)

.github/workflows/validate.yml

@@ -40,6 +40,17 @@ jobs:
         os: ["ubuntu-20.04", "macos-latest", "windows-latest"]
         ghc: ["9.6.1", "9.4.2", "9.2.3", "9.0.2", "8.10.7", "8.8.4", "8.6.5", "8.4.4"]
         exclude:
+          # We have to disable Windows jobs until cabal-install-3.10 is
+          # available through actions on this platform, see
+          # https://github.com/haskell/actions/issues/202#issuecomment-1465856373
+          - os: "windows-latest"
+            ghc: "9.6.1"
+          - os: "windows-latest"
+            ghc: "9.4.2"
+          - os: "windows-latest"
+            ghc: "9.2.3"
+          - os: "windows-latest"
+            ghc: "9.0.2"
           # corrupts GHA cache or the fabric of reality itself, see https://github.com/haskell/cabal/issues/8356
           - os: "windows-latest"
             ghc: "8.10.7"