Use different agent for iOS

Author: aurimasc

.yamato/upm-ci.yml

@@ -125,9 +125,9 @@ test_Android_{{ editor.version }}:
 test_iOS_{{ editor.version }}:
   name: Test {{ editor.version }} on iOS
   agent:
-    type: Unity::mobile::iPhone
-    image: mobile/macos-10.13-testing:stable
-    flavor: b1.medium
+    type: Unity::VM::osx
+    image: mobile/ios-macos-10.15:latest
+    flavor: i1.large
   variables:
     IOS_SIMULATOR_SDK: 1
   commands: