Docs: Update the comment of the `wp_enqueue_classic_theme_styles()` function

[wildworks]

Related to #61892

The wp_enqueue_classic_theme_styles() function is executed on both the editor and the front-end:

• ​Frontend
• ​Editor

Therefore, the following function comment is misleading:

"Loads classic theme styles on classic themes in the frontend."

We should remove the "in the frontend." fron the comment.

[iflairwebtechnologies]

Patch updates incorrect docblock description

[iflairwebtechnologies]

Updates docblock to remove incorrect “in the frontend” reference.

This PR updates the docblock for wp_enqueue_classic_theme_styles() to remove
the incorrect “in the frontend” phrase.

The function is executed on both the editor and the front end.

[manhphucofficial]

Attached a GitHub pull request for this change:

​https://github.com/WordPress/wordpress-develop/pull/10565

[sabernhardt]

When "in the frontend" was added in r54687, there were separate functions for front end and editor, but the editor started adding the stylesheet in the iframe as early as 6.4. (And 6.8 deprecated the editor function in r59980.)

[westonruter]

I think the description might be further improved.

In r54687 the function changed so that it only enqueued in non-block themes. That is, it enqueued in classic and hybrid themes. Now, however, it's enqueueing only in themes that lack a theme.json, which would be exclusively classic non-hybrid themes. It uses wp_theme_has_theme_json() which “Checks whether a theme or its parent has a theme.json file.” Since the definition of "classic theme" often encompases hybrid themes, I think this can be more explicit. So instead of:

Loads classic theme styles on classic themes.

I think it should rather be:

Loads classic theme styles in themes which lack a theme.json file.

Suggested change applied. Let me know if anything else is needed.

Suggested change applied. Thanks for the clarification!

[westonruter]

In 61322:

Docs: Improve accuracy of wp_enqueue_classic_theme_styles() description.

Developed in ​https://github.com/WordPress/wordpress-develop/pull/10565

Follow-up to [59980], [54687], [54358].

Props manhphucofficial, wildworks, sabernhardt, iflairwebtechnologies, westonruter.
See #61892, #64224.
Fixes #64317.