stream_edit: Remove unused import.
stream_edit: Remove unused import.

This was introduced when rebasing
d62e44fcba96286696cbd296e3f3ef7de8d9c1cb on top of
8cc781f0c8ece64d6a40e926f5660e74aecb12d5, which removed the other use
of this module in this file.

eeshangarg/zulip,zulip/zulip,rht/zulip,andersk/zulip,andersk/zulip,zulip/zulip,andersk/zulip,zulip/zulip,eeshangarg/zulip,andersk/zulip,zulip/zulip,kou/zulip,rht/zulip,zulip/zulip,eeshangarg/zulip,rht/zulip,andersk/zulip,rht/zulip,kou/zulip,kou/zulip,kou/zulip,eeshangarg/zulip,kou/zulip,rht/zulip,kou/zulip,zulip/zulip,eeshangarg/zulip,zulip/zulip,rht/zulip,eeshangarg/zulip,andersk/zulip,eeshangarg/zulip,kou/zulip,rht/zulip,andersk/zulip