update platform from ubuntu-20.04 to ubuntu-latest

Author: deniak

.github/workflows/echidna.yml

@@ -5,7 +5,7 @@ on:
 jobs:
   main:
     name: Build, Validate, and Deploy
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
       - name: Checkout source code
         uses: actions/checkout@v3