Skip problematic expectation on MRI
Skip problematic expectation on MRI

* MRI returns an ICLASS for e.receiver, which is a bug, but the fix is
  not yet backported.

ruby/spec,nobu/rubyspec,eregon/rubyspec,ruby/spec,ruby/spec,ruby/rubyspec,nobu/rubyspec,ruby/rubyspec,eregon/rubyspec,eregon/rubyspec,nobu/rubyspec