Update ghc version for haddocks building on CI

Author: lehins

.github/workflows/gh-pages.yml

@@ -18,7 +18,7 @@ jobs:
       uses: input-output-hk/setup-haskell@v1
       id: setup-haskell
       with:
-        ghc-version: "9.2.8"
+        ghc-version: "9.6.7"
         cabal-version: "3.12"
 
     - name: Install system dependencies