LibWeb: Remove declarations for non-existent methods

Author: https://github.com/AtkinsSJ
Commit: 7891ad2a28
Pull-request: https://github.com/SerenityOS/serenity/pull/17203
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibWeb/HTML/BrowsingContextGroup.h

@@ -27,7 +27,6 @@ public:
     auto const& browsing_context_set() const { return m_browsing_context_set; }
 
     void append(BrowsingContext&);
-    void remove(BrowsingContext&);
 
 private:
     explicit BrowsingContextGroup(Web::Page&);