bump GHC versions in all github workflows

Author: jberthold

.github/workflows/master.yml

@@ -8,7 +8,7 @@ concurrency:
   cancel-in-progress: true
 
 env:
-  ghc_version: "9.6.5"
+  ghc_version: "9.8.4"
   stack_version: "2.15.1"
   hpack_version: '0.36'
 

.github/workflows/release.yml

@@ -5,7 +5,7 @@ on:
       - release
 
 env:
-  ghc_version: "9.6.5"
+  ghc_version: "9.8.4"
   stack_version: "2.15.1"
   hpack_version: '0.36'
 

.github/workflows/test.yml

@@ -10,7 +10,7 @@ concurrency:
   cancel-in-progress: true
 
 env:
-  ghc_version: "9.6.5"
+  ghc_version: "9.8.4"
   stack_version: "2.15.1"
   hpack_version: '0.36'