[CI] Bump haskell-actions to 2.7.6, and actions/cache to 4.1.2

Author: wrengr

.github/workflows/ci.yml

@@ -40,7 +40,7 @@ jobs:
           ghc: 'latest'
     steps:
     - uses: actions/checkout@v4
-    - uses: haskell-actions/[email protected].4
+    - uses: haskell-actions/[email protected].6
       id: setup-haskell-cabal
       with:
         ghc-version: ${{ matrix.ghc }}
@@ -55,7 +55,7 @@ jobs:
     - name: Freeze
       # Generates the `cabal.project.freeze` file.
       run: cabal freeze
-    - uses: actions/cache@v4.0.2
+    - uses: actions/cache@v4.1.2
       name: Cache ~/.cabal/store and ./dist-newstyle
       # TODO(2021-10-23): Do we really want the hash in the key?
       #   With nix-style builds it shouldn't be necessary (afaict),