Remove JWT auth plugin integration

[joshcanhelp]

Changes

This is a potential breaking change for developers!

• Remove WP_Auth0_Configure_JWTAUTH class
• Remove public WP_Auth0_UsersRepo::init() method
• Remove public WP_Auth0_UsersRepo::getUser() method
• Remove public WP_Auth0_UsersRepo::tokenHasRequiredScopes() method
• Remove public WP_Auth0_Admin_Advanced::render_jwt_auth_integration() method and associated validation
• Change WP_Auth0_Settings_Section constructor to remove WP_Auth0_Configure_JWTAUTH argument

Note to reviewers: As usual, POT, PO, and MO files can be ignored, just removing now-unused translation strings.

Testing

• This change adds unit test coverage
• This change has been tested on WP 5.2.2

Checklist

• All existing and new tests complete without errors
• All code quality tools/guidelines in the Contribution guide have been run/followed
• All active GitHub CI checks have passed