Use WordPress Libraries 1.3.0

[n7studios]

Summary

Updates the Plugin to use the latest version of our ConvertKit WordPress Libraries, 1.3.0, which contains the necessary API functions for the Restrict Content functionality.

Adding this prior to Restrict Content functionality in the main ConvertKit Plugin so we avoid a repeat of this issue.

Testing

Existing tests pass.

Checklist

• [x] I have written a test and included it in this PR
• [x] I have run all tests and they pass
• [x] The code passes when running the PHP CodeSniffer
• [x] Code meets WordPress Coding Standards for PHP, HTML, CSS and JS
• [x] Security and Sanitization requirements have been followed
• [x] I have assigned a reviewer or two to review this PR (if you're not sure who to assign, we can do this step for you)