Update actions/cache action to v6

Update actions/cache from 5.1.0 to 6.1.0

Change-type: patch

Author: balena-renovate[bot]

.github/workflows/link-checker.yml

@@ -27,7 +27,7 @@ jobs:
 
       - name: Restore lychee cache
         id: restore-cache
-        uses: actions/cache/restore@caa296126883cff596d87d8935842f9db880ef25 # v5.1.0
+        uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
         with:
           path: .lycheecache
           key: cache-lychee-${{ github.sha }}
@@ -57,7 +57,7 @@ jobs:
             automated issue
 
       - name: Save lychee cache
-        uses: actions/cache/save@caa296126883cff596d87d8935842f9db880ef25 # v5.1.0
+        uses: actions/cache/save@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
         if: ! cancelled()
         with:
           path: .lycheecache