Fix deprecated actions/cache SHA (v2->v4)

Author: Jonathan D.A. Jewell

.github/workflows/casket-pages.yml

@@ -35,7 +35,7 @@ jobs:
           cabal-version: '3.10'
 
       - name: Cache Cabal
-        uses: actions/cache@0c45773b623bea8c8e75f6c82b208c3cf94ea4f9 # v4
+        uses: actions/cache@0057852bfaa89a56745cba8c7296529d2fc39830 # v4
         with:
           path: |
             ~/.cabal/packages