Updates: target sdk version to 31

[AjeshRPai]

Closes #1003

This PR updates the targetSDKversion to 31 for the Android 12 migration

Test Instructions

• Install the app from the Parent https://github.com/wordpress-mobile/WordPress-Android/pull/17153
• Make sure the functionalities provided by the library work as expected

[x] If there are new strings that have to be translated, I have added them to the client's strings.xml as a part of the integration PR.