set ubuntu to 20.04

Author: CodeByDrescher

.github/workflows/buildDockerImage.yml

@@ -12,7 +12,7 @@ jobs:
   buildAndPushImage:
     name: Build and push Docker image
     if: "!contains(github.event.head_commit.message, '[skip ci]') && github.actor != 'allcontributors'"
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
 
     steps:
       # Free disk space