Removes unnecessary "new" in documentation (#29779)

diff --git a/packages/flutter_localizations/lib/src/l10n/README.md b/packages/flutter_localizations/lib/src/l10n/README.md
index 8998bad..bcd4cdb 100644
--- a/packages/flutter_localizations/lib/src/l10n/README.md
+++ b/packages/flutter_localizations/lib/src/l10n/README.md
@@ -41,8 +41,8 @@
 
 ```dart
 Widget build(BuildContext context) {
-  return new FlatButton(
-    child: new Text(
+  return FlatButton(
+    child: Text(
       MaterialLocalizations.of(context).cancelButtonLabel,
     ),
   );