Remove Earl Grey matcher APIs taking NSString.

ios/web/public/test/earl_grey/web_view_matchers.mm

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/web/public/test/earl_grey/web_view_matchers.h"
 
 #import <WebKit/WebKit.h>
 
 #include "base/mac/bind_objc_block.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/test/ios/wait_util.h"
 #include "base/values.h"
 #include "ios/testing/earl_grey/wait_util.h"
 
 namespace {
 
 // Script that returns document.body as a string.
 char kGetDocumentBodyJavaScript[] =
     "document.body ? document.body.textContent : null";
 }
 
 namespace web {
 
-id<GREYMatcher> webViewContainingText(NSString* text, web::WebState* webState) {
-  return [GREYMatchers
-      matcherForWebViewContainingText:base::SysNSStringToUTF8(text)
-                           inWebState:webState];
-}
-
 id<GREYMatcher> webViewContainingText(const std::string& text,
                                       web::WebState* webState) {
   return
       [GREYMatchers matcherForWebViewContainingText:text inWebState:webState];
 }
 
 }  // namespace web
 
 @implementation GREYMatchers (WebViewAdditions)
 
@@ skipping 31 matching lines @@
     [description appendText:@"web view containing "];
     [description appendText:base::SysUTF8ToNSString(text)];
   };
 
   return [[[GREYElementMatcherBlock alloc] initWithMatchesBlock:matches
                                                descriptionBlock:describe]
       autorelease];
 }
 
 @end