Upgrade actions. (#283)

Author: jonathanknowles

.github/workflows/build.yml

@@ -35,7 +35,7 @@ jobs:
           - '9.12'
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Environment
         uses: haskell-actions/setup@v2
@@ -60,7 +60,7 @@ jobs:
           --builddir=${{ env.cabal-build-dir }}
 
       - name: Cache
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         env:
           hash: ${{ hashFiles('cabal.project.freeze') }}
         with: