.bashrc.d/00environment: Disable update-notifier checks

.bashrc.d/00environment: Disable update-notifier checks

I don't care if my local Yeoman, Bower, ..., is out of date (certainly
not enough for a network ping on each invocation).  I'll update my
tools periodically on my own.  From [1]:

  Users can also opt-out by setting the environment variable
  NO_UPDATE_NOTIFIER with any value.

[1]: https://github.com/yeoman/update-notifier