Bump actions/checkout from 3 to 4

.github/workflows/check_md_links.yml

@@ -6,5 +6,5 @@ jobs:
   markdown-link-check:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - uses: gaurav-nelson/github-action-markdown-link-check@v1

.github/workflows/publishdocs.yaml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout master
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Deploy docs
         uses: mhausenblas/mkdocs-deploy-gh-pages@master

.github/workflows/test_and_coverage.yml

@@ -20,7 +20,7 @@ jobs:
     steps:
 
     - name: Clone repo
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
 
     - name: Set up Python
       uses: actions/setup-python@v4

.github/workflows/validate.yml

@@ -20,7 +20,7 @@ jobs:
           node-version: "12.x"
 
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       # Checks that our JSON are valid
       - name: Check for syntax errors