I18N: Add type declaration to new method missed in [57518].

See #59656.
Built from https://develop.svn.wordpress.org/trunk@57519


git-svn-id: http://core.svn.wordpress.org/trunk@57020 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/l10n/class-wp-translation-file.php

@@ -247,7 +247,7 @@ abstract class WP_Translation_File {
 	 * @param string $header Plural-Forms header string.
 	 * @return string Plural forms expression.
 	 */
-	protected function get_plural_expression_from_header( $header ) {
+	protected function get_plural_expression_from_header( string $header ): string {
 		if ( preg_match( '/^\s*nplurals\s*=\s*(\d+)\s*;\s+plural\s*=\s*(.+)$/', $header, $matches ) ) {
 			return trim( $matches[2] );
 		}

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.5-alpha-57518';
+$wp_version = '6.5-alpha-57519';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.