Updated version of actions/checkout

Author: AdamVyborny

.github/workflows/push.yml

@@ -16,7 +16,7 @@ jobs:
     steps:
       -
         name: 'Check out the repo'
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       -
         name: 'Docker login'
         if: env.DOCKERHUB_TOKEN