Fix Button Heights in WordPress 7.0

[n7studios]

Summary

Fixes button heights in the settings screens when using WordPress 7.0, and standardises them across 6.x and 7.x.

WordPress 7.0 before:

WordPress 6.9 before:

WordPress 7.0 after:

WordPress 6.9 after:

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)