Unable to defer scripts using Wordpress 6.3+

[harlessmark]

Description of the bug

With Wordpress version >= 6.3.0, using am_modify_load_method results in the expected attribute not being added.

In this if statement, since I am always going to be using Wordpress version 6.3+, the defer string will never be added to $load_methods_to_async, so in turn will never be added to async_scripts, so in turn will never add the attribute to the tag.

Steps To Reproduce

On Wordpress 6.3 or greater, attempt to modify the load method for a script as documented.

// Defer an enqueued JavaScript asset.
am_modify_load_method(
  [
    'handle'      => 'footer-script', 
    'load_method' => 'defer',
  ]
);

Expected: The defer attribute is present on the script tag in the DOM
Actual: The defer attribute is missing from the script tag

Additional Information

We tried using the async-defer load method as a workaround, but that prints an enqueue error stating "there is no guarantee it will be available for its dependent asset.”

Acceptance Criteria

• Set the minimum required version of WordPress to 6.3.
• Use the new script loading features available in 6.3 without condition checks.
• Ensure there is a unit test that covers this use case and that it passes.
• Release this update alongside Remove the 'async-defer' load method #63 in a new v2.0.0 as a breaking change.