Do not include object string representation in `NoMethodError` message.

This information is not mandatory but causes a lot of problems in the
past due to infinite recursion by redefining `to_str`, `inspect` etc.

src/kernel.c

@@ -956,26 +956,7 @@ mrb_obj_remove_instance_variable(mrb_state *mrb, mrb_value self)
 void
 mrb_method_missing(mrb_state *mrb, mrb_sym name, mrb_value self, mrb_value args)
 {
-  mrb_sym inspect;
-  mrb_value repr;
-
-  inspect = mrb_intern_lit(mrb, "inspect");
-  if (mrb->c->ci > mrb->c->cibase && mrb->c->ci[-1].mid == inspect) {
-    /* method missing in inspect; avoid recursion */
-    repr = mrb_any_to_s(mrb, self);
-  }
-  else if (mrb_respond_to(mrb, self, inspect) && mrb->c->ci - mrb->c->cibase < 16) {
-    repr = mrb_funcall_argv(mrb, self, inspect, 0, 0);
-    if (mrb_string_p(repr) && RSTRING_LEN(repr) > 64) {
-      repr = mrb_any_to_s(mrb, self);
-    }
-  }
-  else {
-    repr = mrb_any_to_s(mrb, self);
-  }
-
-  mrb_no_method_error(mrb, name, args, "undefined method '%S' for %S",
-                      mrb_sym2str(mrb, name), repr);
+  mrb_no_method_error(mrb, name, args, "undefined method '%S'", mrb_sym2str(mrb, name));
 }
 
 /* 15.3.1.3.30 */