ci: use node 12

Author: KazuCocoa

ci-jobs/functional/run_appium.yml

@@ -1,8 +1,8 @@
 steps:
 - task: NodeTool@0
   inputs:
-    versionSpec: 10.x
-  displayName: Install Node 10.x
+    versionSpec: 12.x
+  displayName: Install Node 12.x
 - script: npm install -g appium@${APPIUM_VERSION}
   displayName: Install appium beta
 - script: npm install -g mjpeg-consumer