✅🚧 Mark local stacktrace tests pending for JRuby

[nevans]

The stacktraces just don't line up.

• JRuby Issue: raise should re-populate exception trace set to nil jruby/jruby#9528
• Fixed by: raise should re-populate exception trace set to nil jruby/jruby#9528

[nevans]

There are still a couple of issues related to this:

• JRuby's caller(1) differs from (raise rescue $!.backtrace[1..]). (easy workaround)
• There is a deeper issue of exceptions from the receiver thread are sometimes not correctly conveyed to the main thread, which raises IOError instead. This makes the tests flaky when they contain assertions about receiver thread error handling. But I think it's less a flaky test issue and more an actual threading issue in the client code, and it'll be fixed separately.