Bump cache and checkout actions

"Node.js 16 actions are deprecated. Please update the following
actions to use Node.js 20: actions/checkout@v3, actions/cache@v3. For
more information see:
https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/."

.github/workflows/ci.yml

@@ -24,7 +24,7 @@ jobs:
           - "9.8.1"
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
       if: github.event.action == 'opened' || github.event.action == 'synchronize' || github.event.ref == 'refs/heads/main'
 
     - uses: haskell-actions/[email protected]
@@ -33,7 +33,7 @@ jobs:
         ghc-version: ${{ matrix.ghc }}
         cabal-version: ${{ matrix.cabal }}
 
-    - uses: actions/cache@v3
+    - uses: actions/cache@v4
       name: Cache ~/.cabal/store
       with:
         path: ~/.cabal/store