Frontend: Remove -enable-resilient-objc-class-stubs flag

Author: slavapestov

include/swift/Option/FrontendOptions.td

@@ -582,8 +582,4 @@ def type_info_dump_filter_EQ : Joined<["-"], "type-info-dump-filter=">,
   Flags<[FrontendOption]>,
   HelpText<"One of 'all', 'resilient' or 'fragile'">;
 
-def enable_objc_resilient_class_stubs : Flag<["-"], "enable-resilient-objc-class-stubs">,
-  HelpText<"Emit Objective-C resilient class stubs for classes with "
-           "resiliently-sized metadata">;
-
 } // end let Flags = [FrontendOption, NoDriverOption, HelpHidden]