Summary

#982 and #985 upgraded the Plugin's blocks to the block apiVersion 2 and 3 respectively, depending on the WordPress version. However, this is insufficient, as registerBlockType must also specify the apiVersion, which this PR resolves.

registerBlockType does support passing the metadata object loaded from our block.json definitions, which will be addressed in a future PR when our JS build work extends to the backend scripts.

Testing

Existing tests pass.

Checklist

• I have written a test and included it in this PR
• I have run all tests and they pass
• The code passes when running the PHP CodeSniffer
• Code meets WordPress Coding Standards for PHP, HTML, CSS and JS
• Security and Sanitization requirements have been followed
• 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)