[iOS] Removing SyncPresenter from SigninCoordinator

Related to: crrev.com/c/2087617

Fixed: 1046757
Change-Id: I01cd98b6483f21617c97ac92c267e4dd5b6178ad
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2094981
Auto-Submit: Jérôme Lebel <jlebel@chromium.org>
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#748168}

ios/chrome/browser/ui/authentication/signin/signin_coordinator.h

@@ -15,8 +15,6 @@
 class Browser;
 @class ChromeIdentity;
 
-@protocol SyncPresenter;
-
 // Called when the sign-in dialog is closed.
 // |result| is the sign-in result state.
 // |identity| is the identity chosen by the user during the sign-in.