Docs: Standardize references to "meta box" or "meta boxes" as two distinct words throughout core documentation per the core spelling guide.

See #32246.


git-svn-id: https://develop.svn.wordpress.org/trunk@38029 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/media.php

@@ -2818,7 +2818,7 @@ function edit_form_image_editor( $post ) {
 }
 
 /**
- * Displays non-editable attachment metadata in the publish metabox
+ * Displays non-editable attachment metadata in the publish meta box.
  *
  * @since 3.5.0
  */