Update Flask Empower URL

[sdzhong]

android/app/src/main/AndroidManifest.xml

Line 83 in 6d98989

android:value="https://application-monitoring-flask-dot-sales-engineering-sf.appspot.com" />

and

android/app/src/test/java/com/example/vu/android/empowerplant/MainFragmentTest.java

Line 24 in 6d98989

String domain = "https://application-monitoring-flask-dot-sales-engineering-sf.appspot.com";

are outdated.

Update to use https://flask.empower-plant.com URL