chore(deps): update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/check-tag.yml

@@ -9,7 +9,7 @@ jobs:
   check:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
       - name: Run checks
         run: |
           grep -P --color=always "\s+(?<=rev: )$GITHUB_REF_NAME$" README.md

.github/workflows/check.yml

@@ -10,7 +10,7 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
       # No caching as we're expected to run rarely
       - name: Install dependencies and run checks
         run: |