narrow: Remove unused import of stream_topic_history.
narrow: Remove unused import of stream_topic_history.

kou/zulip,andersk/zulip,rht/zulip,kou/zulip,hackerkid/zulip,andersk/zulip,kou/zulip,kou/zulip,hackerkid/zulip,zulip/zulip,andersk/zulip,rht/zulip,punchagan/zulip,punchagan/zulip,kou/zulip,zulip/zulip,andersk/zulip,eeshangarg/zulip,rht/zulip,hackerkid/zulip,punchagan/zulip,eeshangarg/zulip,kou/zulip,hackerkid/zulip,zulip/zulip,punchagan/zulip,zulip/zulip,kou/zulip,zulip/zulip,eeshangarg/zulip,hackerkid/zulip,rht/zulip,rht/zulip,hackerkid/zulip,eeshangarg/zulip,eeshangarg/zulip,eeshangarg/zulip,andersk/zulip,punchagan/zulip,andersk/zulip,rht/zulip,hackerkid/zulip,punchagan/zulip,punchagan/zulip,andersk/zulip,eeshangarg/zulip,zulip/zulip,rht/zulip,zulip/zulip