Update base image

Beat Buesser · Beat Buesser · commit bbc53e640153 · 2021-09-23T00:04:19.000+01:00
Signed-off-by: Beat Buesser &lt;beat.buesser@ie.ibm.com&gt;
diff --git a/.github/workflows/ci-legacy.yml b/.github/workflows/ci-legacy.yml
@@ -20,7 +20,7 @@ on:
 
 jobs:
   test:
-    runs-on: ubuntu-16.04
+    runs-on: ubuntu-20.04
     strategy:
       fail-fast: false
       matrix:
diff --git a/.github/workflows/ci-mxnet.yml b/.github/workflows/ci-mxnet.yml
@@ -20,7 +20,7 @@ on:
 
 jobs:
   test:
-    runs-on: ubuntu-16.04
+    runs-on: ubuntu-18.04
     strategy:
       fail-fast: false
       matrix:
