fix: Correct help text formatting for adk deploy agent_engine

[hangfei]

The Args: section in the docstring of the cli_deploy_agent_engine function was causing formatting issues in the help output, with line breaks not being rendered correctly.

This commit removes the redundant Args: section from the docstring. The help text for options is already comprehensively covered by the help attributes in the @click.option decorators, and click automatically lists the command's arguments.

This change ensures that the help output for
adk deploy agent_engine --help is clean, readable, and correctly formatted, relying on click's standard help generation mechanisms.

After the fix:

(adk_test234) (base) hangfeilin@Hangfeis-MBP adk-python % adk deploy agent_engine --help
Usage: adk deploy agent_engine [OPTIONS] AGENT

Deploys an agent to Agent Engine.

Args: agent (str): Required. The path to the agent to be deloyed.

Example:

adk deploy agent_engine --project=[project] --region=[region]     --staging_bucket=[staging_bucket] path/to/my_agent

Options:
--project TEXT Required. Google Cloud project to deploy the agent.
--region TEXT Required. Google Cloud region to deploy the agent.
--staging_bucket TEXT Required. GCS bucket for staging the deployment artifacts.
--trace_to_cloud Optional. Whether to enable Cloud Trace for Agent Engine.
--adk_app TEXT Optional. Python file for defining the ADK application (default: a file named agent_engine_app.py)
--temp_folder TEXT Optional. Temp folder for the generated Agent Engine source files. If the folder already exists, its
contents will be removed. (default: a timestamped folder in the system temp directory).
--env_file TEXT Optional. The filepath to the .env file for environment variables. (default: the .env file in
the agent directory, if any.)
--requirements_file TEXT Optional. The filepath to the requirements.txt file to use. (default: the requirements.txt file
in the agent directory, if any.)
--help Show this message and exit.

[hangfei]

Click tools doesn't render line break for each line in the docstring. So to add a line break, a new line need to be placed between args.

However, we already have help text for each options so we should remove those redundant doc string.

Click args, by design or follow unix convention, doesn't have help text and should be documented in the docstring instead.