[iOS] Fixes Incognito badge colour

Disabled buttons are greyed out.
This CL sets the button's property |userInteractionEnabled| to NO instead of disabling it.

Bug: 1106673
Change-Id: I56d877a88cbb44313225ee5bfa76f73590883d67
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2343073
Auto-Submit: Ewann Pellé <ewannpv@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#795929}

ios/chrome/browser/ui/badges/badge_button_factory.mm

@@ -113,7 +113,7 @@
       [UIColor colorNamed:kTextPrimaryColor], self.incognito,
       [UIColor colorNamed:kTextPrimaryDarkColor]);
   button.accessibilityTraits &= ~UIAccessibilityTraitButton;
-  button.enabled = NO;
+  button.userInteractionEnabled = NO;
   button.accessibilityIdentifier = kBadgeButtonIncognitoAccessibilityIdentifier;
   button.accessibilityLabel =
       l10n_util::GetNSString(IDS_IOS_BADGE_INCOGNITO_HINT);