ci: Remove matrix build for GHC 9.4.8 via Cabal on Linux

This is to reduce storage requirements for GitHub Actions cache. We already build with GHC 9.4.x
via Nix on Linux x64, via stack on FreeBSD, MacOS and Windows and via Cabal on Linux ARM. That
should cover 9.4.x enough.

.github/workflows/build.yaml

@@ -152,7 +152,7 @@ jobs:
   cabal:
     strategy:
       matrix:
-        ghc: ['9.4.8', '9.6.4', '9.8.2']
+        ghc: ['9.6.4', '9.8.2']
       fail-fast: false
     name: Cabal - Linux GHC ${{ matrix.ghc }}
     runs-on: ubuntu-latest