Bump Haskell CI to GHC 9.12

Author: andreasabel

cpphs.cabal

@@ -25,9 +25,10 @@ Build-type: Simple
 Extra-Source-Files: README, LICENCE-GPL, LICENCE-commercial, CHANGELOG, docs/cpphs.1, docs/index.html
 
 tested-with:
-  GHC == 9.10.1
-  GHC == 9.8.2
-  GHC == 9.6.6
+  GHC == 9.12.2
+  GHC == 9.10.2
+  GHC == 9.8.4
+  GHC == 9.6.7
   GHC == 9.4.8
   GHC == 9.2.8
   GHC == 9.0.2