Fix DefaultLoginPageGeneratingFilter Markup

the `</h3>` should be `</h2>`.

web/src/main/java/org/springframework/security/web/authentication/ui/DefaultLoginPageGeneratingFilter.java

@@ -272,7 +272,7 @@ public class DefaultLoginPageGeneratingFilter extends GenericFilterBean {
 		}
 
 		if (oauth2LoginEnabled) {
-			sb.append("<h2 class=\"form-signin-heading\">Login with OAuth 2.0</h3>");
+			sb.append("<h2 class=\"form-signin-heading\">Login with OAuth 2.0</h2>");
 			sb.append(createError(loginError, errorMsg));
 			sb.append(createLogoutSuccess(logoutSuccess));
 			sb.append("<table class=\"table table-striped\">\n");