non-ASCII characters are escaped in telemetry trace_send_data

[genkey6]

Describe the bug
In the trace_send_data function of the telemetry module, the JSON-dumped content is set as an attribute of the span.
When non-ASCII characters (such as Japanese Hiragana or Kanji) are passed to the function, they are escaped in the exported span logs.

Expected behavior
Non-ASCII characters (such as Japanese Hiragana or Kanji) should be preserved in their original form in the exported span logs, without being escaped.
For example, the string "こんにちは" should appear as "こんにちは" in the span attributes, not as escaped Unicode like "\u3053\u3093\u306b\u3061\u306f".

Desktop (please complete the following information):

• Python version(python -V): 3.12.9
• ADK version(pip show google-adk): 1.1.1