ci: use ubuntu 18.04 for arm testing (#14988)

Dockerfile.arm32v7

@@ -1,4 +1,4 @@
-FROM arm32v7/ubuntu:16.04
+FROM arm32v7/ubuntu:18.04
 
 RUN groupadd --gid 1000 builduser \
   && useradd --uid 1000 --gid builduser --shell /bin/bash --create-home builduser

vsts-arm32v7.yml

@@ -1,7 +1,7 @@
 resources:
   containers:
   - container: arm32v7-test-container
-    image: electronbuilds/arm32v7:0.0.1
+    image: electronbuilds/arm32v7:0.0.2
 
 jobs:
 - job: Test_Arm32v7