[BUG, pkg-py]: False-positive deprecation warning

[cpsievert]

#91 introduced a false-positive deprecation when input is submitted:

import shiny.express

from shinychat.express import Chat

chat = Chat(id="chat")
chat.ui()

@chat.on_user_submit
async def handle_user_input(user_input: str):
    await chat.append_message(f"You said: {user_input}")

ShinyDeprecationWarning: `.user_input(transform=...)` is deprecated. User input transformation features will be removed in a future version. See here for more details: https://github.com/posit-dev/shinychat/pull/91
  input = self.user_input(transform=True)