Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/documentation.yml

@@ -12,7 +12,7 @@ jobs:
     if: github.event_name != 'push'
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - uses: actions/setup-node@v2
         with:
           node-version: '16.x'
@@ -30,7 +30,7 @@ jobs:
     if: github.event_name != 'pull_request'
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - uses: actions/setup-node@v2
         with:
           node-version: '16.x'