Themes: Remove mention of “FSE” in Core.

Props aristath, jorbin.
Fixes #53497.
Built from https://develop.svn.wordpress.org/trunk@51251


git-svn-id: http://core.svn.wordpress.org/trunk@50860 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/customize.php

@@ -186,7 +186,7 @@ do_action( 'customize_controls_head' );
 			$compatible_php = is_php_version_compatible( $wp_customize->theme()->get( 'RequiresPHP' ) );
 			$fse_safe       = true;
 
-			// Check if the theme requires the FSE to work correctly.
+			// Check if the theme requires the Gutenberg plugin to work correctly.
 			$theme_tags = $wp_customize->theme()->get( 'Tags' );
 
 			if ( ! empty( $theme_tags ) && in_array( 'full-site-editing', $theme_tags, true ) && ! function_exists( 'gutenberg_is_fse_theme' ) ) {

wp-includes/theme.php

@@ -913,7 +913,7 @@ function validate_theme_requirements( $stylesheet ) {
 
 	if ( ! empty( $theme_tags ) && in_array( 'full-site-editing', $theme_tags, true ) && ! function_exists( 'gutenberg_is_fse_theme' ) ) {
 		return new WP_Error(
-			'theme_requires_fse',
+			'theme_requires_gutenberg_plugin',
 			sprintf(
 					/* translators: %s: Theme name. */
 				_x( '<strong>Error:</strong> This theme (%s) uses Full Site Editing, which requires the Gutenberg plugin to be activated.', 'theme' ),

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.8-beta4-51250';
+$wp_version = '5.8-beta4-51251';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.