(actions) run on 20.04

Author: MatthijsBurgh

.github/workflows/main.yml

@@ -13,7 +13,7 @@ defaults:
 jobs:
   deployment:
     name: deployment
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v2
       - name: Install