IWYU: Removed some unnecessary includes (mailto_handler*)

Review-Url: https://codereview.chromium.org/2898483002
Cr-Commit-Position: refs/heads/master@{#473322}

ios/chrome/browser/web/mailto_handler_gmail.mm

@@ -3,9 +3,6 @@
 // found in the LICENSE file.
 
 #import "ios/chrome/browser/web/mailto_handler_gmail.h"
-#include "base/strings/sys_string_conversions.h"
-#include "url/gurl.h"
-#include "url/url_constants.h"
 
 #import <UIKit/UIKit.h>
 

ios/chrome/browser/web/mailto_handler_gmail_unittest.mm

@@ -6,7 +6,6 @@
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/gtest_mac.h"
-#include "url/gurl.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."