deps: update actions/cache action to v6 (#884)

Author: renovate[bot]

.github/workflows/links.yml

@@ -13,7 +13,7 @@ jobs:
     steps:
       - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
 
-      - uses: actions/cache@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5
+      - uses: actions/cache@2c8a9bd7457de244a408f35966fab2fb45fda9c8 # v6
         with:
           path: .lycheecache
           key: cache-lychee-${{ github.sha }}