This condition does not seem necessary anymore. Fixes #3008.

I believe this condition was added by @tdeuhr before he adjusted
the lookup logic to work like MRI. Without it, all tests and specs
appear to pass as before, and the error from #3008 goes away.

core/src/main/java/org/jruby/ir/runtime/IRRuntimeHelpers.java

@@ -922,7 +922,7 @@ public static IRubyObject unresolvedSuper(ThreadContext context, IRubyObject sel
         DynamicMethod method = superClass != null ? superClass.searchMethod(methodName) : UndefinedMethod.INSTANCE;
 
         IRubyObject rVal = null;
-        if (method.isUndefined()|| (superClass.isPrepended() && (method.isImplementedBy(self.getType())))) {
+        if (method.isUndefined()) {
             rVal = Helpers.callMethodMissing(context, self, method.getVisibility(), methodName, CallType.SUPER, args, block);
         } else {
             rVal = method.call(context, self, superClass, methodName, args, block);