Updates react-native-aztec android to use S3 dependency for Aztec editor

[oguzkocer]

Description

wordpress-mobile/AztecEditor-Android#941 adds support for publishing AztecEditor-Android to our s3 maven repository. This PR updates react-native-aztec android library to fetch this dependency from S3 instead of Jitpack. It also re-orders to repositories for react-native-aztec so we don't depend on deprecated jcenter repository for any dependency that's published elsewhere.

I'll create a new v1.4 tag for the AztecEditor-Android library and update react-native-aztec before we merge this in.

How has this been tested?

I've tested the WPAndroid integration wordpress-mobile/WordPress-Android#15457 and I was hoping @mchowning could help me test the demo app.

Types of changes

Build file changes for react-native-aztec android.

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR (please manually search all *.native.js files for terms that need renaming or removal).

[mchowning]

Looks good! 👍