arcyon comment: BREAK: don't print result

The result doesn't contain any useful information and exposes conduit
implementation details, which people may come to depend on.

The useful information is the exit code of the program and any error
information.

Test Plan:
$ ./precommit.sh
arcyon comment: use phlcon_differential.createc...

Use phlcon_differential.create_comment() to create comments, this means
that 'arcyon comment' automatically has backwards-compatability with
older versions of Phabricator. Older versions of Phabricator don't
support the 'attach_inlines' parameter.

Test Plan:
$ ./precommit.sh
.. successfully arcyon comment on an old version of Phabricator ..