api: Remove unnecessary API key details.

Fixes #1.

zulip/examples/print-events

@@ -26,13 +26,13 @@ import argparse
 
 from typing import Any, Dict
 
-usage = """print-events --user=<bot's email address> --api-key=<bot's api key> [options]
+usage = """print-events [options]
 
 Prints out certain events received by the indicated bot or user matching the filter below.
 
-Example: print-events --user=username@example.com --api-key=a0b1c2d3e4f5a6b7c8d9e0f1a2b3c4d5
+Example: print-events
 
-You can omit --user and --api-key arguments if you have a properly set up ~/.zuliprc
+Specify your Zulip API credentials and server in a ~/.zuliprc file or using the options.
 """
 
 import zulip