Document EdgeExecutor migration from internal_api_secret_key to jwt_secret

[bdsoha]

This PR updated the documentation to use the new [api_auth] jwt_secret required configuration for EdgeExecutor instead of the old internal_api_secret_key.

Without it, the following error is emitted:

 ____________       _____________
 ____    |__( )_________  __/__  /________      __
____  /| |_  /__  ___/_  /_ __  /_  __ \_ | /| / /
___  ___ |  / _  /   _  __/ _  / / /_/ /_ |/ |/ /
 _/_/  |_/_/  /_/    /_/    /_/  \____/____/|__/
   ____   __           _      __         __
  / __/__/ /__ ____   | | /| / /__  ____/ /_____ ____
 / _// _  / _ `/ -_)  | |/ |/ / _ \/ __/  '_/ -_) __/
/___/\_,_/\_, /\__/   |__/|__/\___/_/ /_/\_\\__/_/
         /___/
Traceback (most recent call last):
  File "/home/airflow/.local/bin/airflow", line 8, in <module>
    sys.exit(main())
             ^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/__main__.py", line 55, in main
    args.func(args)
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/utils/cli.py", line 112, in wrapper
    return f(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/utils/providers_configuration_loader.py", line 55, in wrapped_function
    return func(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/edge3/cli/edge_command.py", line 522, in worker
    run_command_with_daemon_option(
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/cli/commands/daemon_utils.py", line 86, in run_command_with_daemon_option
    callback()
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/edge3/cli/edge_command.py", line 525, in <lambda>
    callback=lambda: _launch_worker(args),
                     ^^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/utils/providers_configuration_loader.py", line 55, in wrapped_function
    return func(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/edge3/cli/edge_command.py", line 513, in _launch_worker
    edge_worker.start()
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/edge3/cli/edge_command.py", line 337, in start
    self.last_hb = worker_register(
                   ^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/edge3/cli/api_client.py", line 119, in worker_register
    result = _make_generic_request(
             ^^^^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/tenacity/__init__.py", line 338, in wrapped_f
    return copy(f, *args, **kw)
           ^^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/tenacity/__init__.py", line 477, in __call__
    do = self.iter(retry_state=retry_state)
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/tenacity/__init__.py", line 378, in iter
    result = action(retry_state)
             ^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/tenacity/__init__.py", line 400, in <lambda>
    self._add_action_func(lambda rs: rs.outcome.result())
                                     ^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/concurrent/futures/_base.py", line 449, in result
    return self.__get_result()
           ^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/concurrent/futures/_base.py", line 401, in __get_result
    raise self._exception
  File "/home/airflow/.local/lib/python3.12/site-packages/tenacity/__init__.py", line 480, in __call__
    result = fn(*args, **kwargs)
             ^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/edge3/cli/api_client.py", line 91, in _make_generic_request
    generator = jwt_generator()
                ^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/edge3/cli/api_client.py", line 85, in jwt_generator
    return JWTGenerator(
           ^^^^^^^^^^^^^
  File "<attrs generated methods airflow.api_fastapi.auth.tokens.JWTGenerator>", line 34, in __init__
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/api_fastapi/auth/tokens.py", line 417, in __attrs_post_init__
    raise ValueError("Exactly one of private_key and secret_key must be specified")
ValueError: Exactly one of private_key and secret_key must be specified

---

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