Update actions/cache for our CI actions are erroring and it seems the

version 2 is no longer supported.

Author: diogob

.github/workflows/ci.yml

@@ -37,7 +37,7 @@ jobs:
       with:
         ghc-version: ${{ matrix.ghc }}
 
-    - uses: actions/cache@v2.1.3
+    - uses: actions/cache@v4
       name: Cache ~/dist-newstyle
       with:
         path: ~/dist-newstyle

.github/workflows/release.yml

@@ -37,7 +37,7 @@ jobs:
       with:
         ghc-version: ${{ matrix.ghc }}
 
-    - uses: actions/cache@v2.1.3
+    - uses: actions/cache@v4
       name: Cache ~/dist-newstyle
       with:
         path: ~/dist-newstyle