docs: use actions/checkout@v4

Signed-off-by: Aleksei Igrychev <aleksei.igrychev@palark.com>

README.md

@@ -16,7 +16,7 @@ converge:
   steps:
 
     - name: Checkout code
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
     
@@ -71,7 +71,7 @@ Make sure to use `fetch-depth: 0` setting in the checkout action, like follows:
 
 ```yaml
 - name: Checkout code
-  uses: actions/checkout@v3
+  uses: actions/checkout@v4
   with:
     fetch-depth: 0
 ```