Update checkout action reference from 4.2 to 4.3

Author: koromerzhin

.github/workflows/ci.yml

@@ -36,7 +36,7 @@ jobs:
         with:
           submodules: recursive
           repository: koromerzhin/lampy
-          ref: '4.2'
+          ref: '4.3'
           path: lampy
 
       - name: Setup cache