Docs: Provide a more accurate description for a few script and style functions.

This should make it clear that the functions only work if the script or style has already been registered.

This affects:
* `wp_localize_script()`
* `wp_set_script_translations()`
* `wp_script_add_data()`
* `wp_style_add_data()`

Follow-up to [7970], [18464], [25594], [31223], [36633], [44169], [44350].

Props audrasjb.
Fixes #54044.

git-svn-id: https://develop.svn.wordpress.org/trunk@51726 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/functions.wp-styles.php

@@ -217,7 +217,7 @@ function wp_style_is( $handle, $list = 'enqueued' ) {
 /**
  * Add metadata to a CSS stylesheet.
  *
- * Works only if the stylesheet has already been added.
+ * Works only if the stylesheet has already been registered.
  *
  * Possible values for $key and $value:
  * 'conditional' string      Comments for IE 6, lte IE 7 etc.