flutter: Change menu text from 'Start new game' to 'New game'

src/ui/flutter_app/lib/l10n/intl_de.arb

@@ -200,9 +200,9 @@
   "@thinking": {
     "description": "Thinking..."
   },
-  "newGame": "Los",
+  "newGame": "Neues Spiel",
   "@newGame": {
-    "description": "Start"
+    "description": "New game"
   },
   "startNewGame": "Beginne ein neues Spiel",
   "@startNewGame": {

src/ui/flutter_app/lib/l10n/intl_en.arb

@@ -200,9 +200,9 @@
   "@thinking": {
     "description": "Thinking..."
   },
-  "newGame": "Start",
+  "newGame": "New game",
   "@newGame": {
-    "description": "Start"
+    "description": "New game"
   },
   "startNewGame": "Start new game",
   "@startNewGame": {

src/ui/flutter_app/lib/l10n/intl_fa.arb

@@ -200,9 +200,9 @@
   "@thinking": {
     "description": "Thinking..."
   },
-  "newGame": "شروع کنید",
+  "newGame": "بازی جدید",
   "@newGame": {
-    "description": "Start"
+    "description": "New game"
   },
   "startNewGame": "شروع بازی جدید",
   "@startNewGame": {

src/ui/flutter_app/lib/l10n/intl_zh.arb

@@ -50,7 +50,7 @@
   "aborted": "中断",
   "draw": "和棋",
   "thinking": "对方思考中...",
-  "newGame": "新局",
+  "newGame": "开始新局",
   "startNewGame": "开始新局",
   "importGame": "导入棋谱",
   "gameImported": "棋谱已从剪贴板导入",

src/ui/flutter_app/lib/widgets/game_page.dart

@@ -671,7 +671,7 @@ class _GamePageState extends State<GamePage>
           children: <Widget>[
             SimpleDialogOption(
               child: Text(
-                S.of(context).startNewGame,
+                S.of(context).newGame,
                 style: AppTheme.simpleDialogOptionTextStyle,
                 textAlign: TextAlign.center,
               ),