fix: remove f-string for enum

[hiohiohio]

fixes #383

Context:

• there is 404 error when subscribe crypto data feed

Changes:

• avoid using f-string for enum

Ref:

• log indicates that enum value is used for f-string replacement for this issue. CryptoFeed.US should be us in the very last line of the below.

  >>> wss_client.run()
  DEBUG:asyncio:Using selector: EpollSelector
  INFO:alpaca.common.websocket:started data stream
  INFO:alpaca.common.websocket:starting data websocket connection
  DEBUG:websockets.client:= connection is CONNECTING
  DEBUG:websockets.client:> GET /v1beta3/crypto/CryptoFeed.US HTTP/1.1

You can test this by

$ docker run -it --entrypoint bash python:3.12-slim
$ apt-get update && apt-get install git -y
$ pip install git+https://github.com/hiohiohio/alpaca-py.git@fix-stream-url-not-found
$ python3

import logging
import sys
logging.basicConfig(stream=sys.stdout, level=logging.DEBUG)

API_KEY=''
SECRET=''
from alpaca.data.live import CryptoDataStream
wss_client = CryptoDataStream(API_KEY, SECRET)

async def bars_data_handler(data):
    print(data)

wss_client.subscribe_bars(bars_data_handler, "BTC/USD")
wss_client.run()