[knowprasad]

Fixes: #789

Summary

In update_message, add_reaction, and remove_reaction, message_id is supplied in the URL path (/messages/{message_id} and /messages/{message_id}/reactions). Because the input dictionary was previously passed directly as the request parameter to call_endpoint, message_id was also forwarded in the request payload, triggering an ignored_parameters_unsupported: ["message_id"] warning response from the Zulip server.

This PR:

• Strips message_id from the forwarded request payload via {k: v for k, v in data.items() if k != "message_id"} in update_message, add_reaction, and remove_reaction.
• Preserves the caller's input dictionary without mutation.
• Adds unit tests in zulip/tests/test_message_endpoints.py asserting that message_id is present in the endpoint URL but excluded from the body payload, and that the original dictionary is unmutated.

How did you test this PR?

Ran pytest locally across the test suite:
pytest zulip/tests/test_message_endpoints.py
All 6 tests passed cleanly.

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