Editor: Remove 'wp-edit-site' stylesheet enqueue from iframe.

Removes enqueuing the `'wp-edit-site'` stylesheet from the iframed assets in `_wp_get_iframed_editor_assets()`.

The global `$pagenow` is also removed as it is no longer used within the function.

References:
* [WordPress/gutenberg#54254 Gutenberg PR 54254]

Props ellatrix, jorgefilipecosta, Mamaduka, mukesh27.

Follow-up to [56047], [53160].
Fixes #59456.

git-svn-id: https://develop.svn.wordpress.org/trunk@56736 602fd350-edb4-49c9-b593-d223f7449a82

Author: hellofromtonya

src/wp-includes/block-editor.php

@@ -287,7 +287,6 @@ function get_legacy_widget_block_editor_settings() {
  * @since 6.0.0
  * @access private
  *
- * @global string     $pagenow    The filename of the current screen.
  * @global WP_Styles  $wp_styles  The WP_Styles current instance.
  * @global WP_Scripts $wp_scripts The WP_Scripts current instance.
  *
@@ -299,7 +298,7 @@ function get_legacy_widget_block_editor_settings() {
  * }
  */
 function _wp_get_iframed_editor_assets() {
-	global $wp_styles, $wp_scripts, $pagenow;
+	global $wp_styles, $wp_scripts;
 
 	// Keep track of the styles and scripts instance to restore later.
 	$current_wp_styles  = $wp_styles;
@@ -329,10 +328,6 @@ function _wp_get_iframed_editor_assets() {
 	// Enqueue the `editorStyle` handles for all core block, and dependencies.
 	wp_enqueue_style( 'wp-edit-blocks' );
 
-	if ( 'site-editor.php' === $pagenow ) {
-		wp_enqueue_style( 'wp-edit-site' );
-	}
-
 	if ( current_theme_supports( 'wp-block-styles' ) ) {
 		wp_enqueue_style( 'wp-block-library-theme' );
 	}