Update actions/checkout action to v4

Author: pschichbot

.github/workflows/generateDocs.yml

@@ -21,7 +21,7 @@ jobs:
 
     # Steps represent a sequence of tasks that will be executed as part of the job
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
           fetch-depth: 0 # otherwise, you will fail to push refs to dest repo