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

Author: renovate[bot]

.github/workflows/validate.yml

@@ -10,7 +10,7 @@ jobs:
   tests:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: actions/setup-node@v4
       with:
         node-version-file: '.nvmrc'
@@ -24,7 +24,7 @@ jobs:
     runs-on: ubuntu-latest
     needs: tests
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Download code coverage results
       uses: actions/download-artifact@v5
       with: