This should cause no functional changes.
This is part of a multi-step effort to move away
from using stream names to reference streams, now
that it's impossible for a user to write a message
with an invalid stream name (since switching to
the dropdown).
This lets us simplify the long-ish ‘../../static/js’ paths, and will
remove the need for the ‘zrequire’ wrapper.
Signed-off-by: Anders Kaseorg <anders@zulip.com>