Suppress TimePicker haptic feedback on iOS (#8347)

State changes are expected to trigger haptic feedback on Android, but
not on iOS time pickers.

packages/flutter/lib/src/material/time_picker.dart

@@ -645,8 +645,19 @@ class _TimePickerDialogState extends State<_TimePickerDialog> {
   _TimePickerMode _mode = _TimePickerMode.hour;
   TimeOfDay _selectedTime;
 
-  void _handleModeChanged(_TimePickerMode mode) {
+  void _vibrate() {
+    switch (Theme.of(context).platform) {
+      case TargetPlatform.android:
+      case TargetPlatform.fuchsia:
         HapticFeedback.vibrate();
+        break;
+      case TargetPlatform.iOS:
+        break;
+    }
+  }
+
+  void _handleModeChanged(_TimePickerMode mode) {
+    _vibrate();
     setState(() {
       _mode = mode;
     });