cleanup: Remove unused imports.

Generated by autoflake.

Signed-off-by: Anders Kaseorg <anders@zulipchat.com>

zulip/zulip/examples/subscribe

@@ -1,6 +1,5 @@
 #!/usr/bin/env python3
 
-import sys
 import argparse
 
 usage = """subscribe [options] --streams=<streams>

zulip/zulip/examples/unsubscribe

@@ -1,6 +1,5 @@
 #!/usr/bin/env python3
 
-import sys
 import argparse
 
 usage = """unsubscribe [options] --streams=<streams>

zulip/zulip/send.py

@@ -5,7 +5,7 @@ import sys
 import argparse
 import logging
 
-from typing import Any, Dict, List, Optional
+from typing import Any, Dict
 
 import zulip