AuthorizationCheckServlet: Add missing serialVersionUID

Change-Id: Ib90c14e5ff4862ca0c608716b6f166957af2965a

java/com/google/gerrit/httpd/raw/AuthorizationCheckServlet.java

@@ -32,6 +32,7 @@ import javax.servlet.http.HttpServletResponse;
  */
 @Singleton
 public class AuthorizationCheckServlet extends HttpServlet {
+  private static final long serialVersionUID = 1L;
   private final Provider<CurrentUser> user;
 
   @Inject