examples/tool-call-stream: Duplicates tool arguments

[tv42]

I think this:

async-openai/examples/tool-call-stream/src/main.rs

Lines 82 to 86 in b26346d

	arguments: tool_call_data
	.function
	.as_ref()
	.and_then(|f| f.arguments.clone())
	.unwrap_or_default(),

and this:

async-openai/examples/tool-call-stream/src/main.rs

Lines 90 to 96 in b26346d

	if let Some(arguments) = tool_call_chunk
	.function
	.as_ref()
	.and_then(|f| f.arguments.as_ref())
	{
	state.function.arguments.push_str(arguments);
	}

store the arguments to a tool call twice. The later call to parse

async-openai/examples/tool-call-stream/src/main.rs

Line 225 in b26346d

let function_args: serde_json::Value = args.parse().unwrap();

fails:

thread 'tokio-runtime-worker' panicked at src/bin/tool-call-stream.rs:243:57:
called `Result::unwrap()` on an `Err` value: Error("trailing characters", line: 1, column: 23)

and printing out args at that point shows

args={"location":"Boston, MA"}{"location":"Boston, MA"}
args={"location":"Atlanta, GA"}{"location":"Atlanta, GA"}

Commenting out the second args storing with push_str fixes the problem.

[mmende]

@tv42 I already made a PR regarding this issue #329