Update actions/cache action to v6 (#668)

Author: renovate[bot]

.github/workflows/additional_checks.yml

@@ -46,7 +46,7 @@ jobs:
           enable-cache: false
       - name: "Cache pre-commit/prek"
         # Not used for releases, only for running pre-commit
-        uses: actions/cache@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5.0.5  # zizmor: ignore[cache-poisoning]
+        uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0  # zizmor: ignore[cache-poisoning]
         with:
           path: |-
             ~/.cache/prek