Remove constants import from unified_consent_view_controller.h

The constants.h import was introduced in crrev/c/1888601 to ensure the
egtest in internal code base can continue accessing the constants. Now
tha egtest in internal code base has been changed to directly import
the constants header in crrev/i/2066050. So the header can be
removed as it's not used in the file.

Bug: 1015907
Change-Id: I6f4be06fd6327ea704012d2bac1e80a59a49bf68
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1893546Reviewed-by: Jérôme Lebel <jlebel@chromium.org>
Commit-Queue: Zhaoyang Li <zhaoyangli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#712645}

ios/chrome/browser/ui/authentication/unified_consent/unified_consent_view_controller.h

@@ -9,8 +9,6 @@
 
 #include <vector>
 
-#import "ios/chrome/browser/ui/authentication/unified_consent/unified_consent_constants.h"
-
 @protocol UnifiedConsentViewControllerDelegate;
 
 // UnifiedConsentViewController is a sub view controller to ask for the user