[ios] Remove extra public keyword from WebState class

Bug: None
Change-Id: I8a464113c62651cba7e18c694097d6f3b7798f74
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2321710Reviewed-by: Ali Juma <ajuma@chromium.org>
Commit-Queue: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#792309}

ios/web/public/web_state.h

@@ -346,7 +346,6 @@ class WebState : public base::SupportsUserData {
   //      the security state (e.g. a non-secure form element is edited).
   virtual void DidChangeVisibleSecurityState() = 0;
 
- public:
   virtual InterfaceBinder* GetInterfaceBinderForMainFrame();
 
   // Whether this WebState was created with an opener.