Just 1 line of code in the webViewDidFinishLoad:(UIWebView *)webView function in the file GTMOAuth2ViewControllerTouch.m

- (void)webViewDidFinishLoad:(UIWebView *)webView {

[self notifyWithName:kGTMOAuth2WebViewStoppedLoading webView:webView kind:kGTMOAuth2WebViewFinished];

// The line of code...
[webView stringByEvaluatingJavaScriptFromString:@"document.getElementById('link-sign-up').style.display = 'none';"];

[...]

Hope it will be enough for Apple.