Upgrade cache action

Author: neilmayhew

.github/workflows/CI.yml

@@ -41,9 +41,7 @@ jobs:
         with:
           ref: main
 
-      # See https://github.com/actions/cache/pull/1231
-      # Astonishingly, this simple bump is not merged and released yet
-      - uses: kbdharun/cache@8070854e57d983bdd2887b0a708ad985f77398ab
+      - uses: actions/cache@v5
         with:
           path: _cache
           key: 1 # bump to refresh