Use old Ubuntu

sverhoeven · sverhoeven · commit ce8074a35094 · 2020-07-01T12:43:49.000+02:00
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
@@ -6,7 +6,7 @@ on:
 
 jobs:
   build:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-16.04
     steps:
     - uses: actions/checkout@v2
     - name: Setup Ruby
