Update actions/checkout action to v6.0.2

Author: AArnott

.github/workflows/docs_validate.yml

@@ -13,7 +13,7 @@ jobs:
     name: 📚 Doc validation
     runs-on: ubuntu-24.04
     steps:
-    - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+    - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
       with:
         fetch-depth: 0 # avoid shallow clone so nbgv can do its work.
     - name: 🔗 Markup Link Checker (mlc)