Source

File: wp-admin/includes/update-core.php

function _upgrade_422_remove_genericons() {
	global $wp_theme_directories, $wp_filesystem;

	// A list of the affected files using the filesystem absolute paths.
	$affected_files = array();

	// Themes.
	foreach ( $wp_theme_directories as $directory ) {
		$affected_theme_files = _upgrade_422_find_genericons_files_in_folder( $directory );
		$affected_files       = array_merge( $affected_files, $affected_theme_files );
	}

	// Plugins.
	$affected_plugin_files = _upgrade_422_find_genericons_files_in_folder( WP_PLUGIN_DIR );
	$affected_files        = array_merge( $affected_files, $affected_plugin_files );

	foreach ( $affected_files as $file ) {
		$gen_dir = $wp_filesystem->find_folder( trailingslashit( dirname( $file ) ) );
		if ( empty( $gen_dir ) ) {
			continue;
		}

		// The path when the file is accessed via WP_Filesystem may differ in the case of FTP.
		$remote_file = $gen_dir . basename( $file );

		if ( ! $wp_filesystem->exists( $remote_file ) ) {
			continue;
		}

		if ( ! $wp_filesystem->delete( $remote_file, false, 'f' ) ) {
			$wp_filesystem->put_contents( $remote_file, '' );
		}
	}
}