[BUG] Saved traces include ndarray objects

[Jgilhuly]

Describe the bug
Traces generated by our Langchain instrumentor and saved via the following code include some ndarray objects:

traces = px.Client().get_trace_dataset(project_name=project_name)
traces.save()

If you then try to load these traces via either the log_traces method or via the --with-trace-fixtures or --with-projects flags, you see the following error:

Error message:
ERROR:phoenix.server.app:Unexpected error processing fixture 'demo_langgraph_agent': Object of type ndarray is not JSON serializable

To Reproduce
Steps to reproduce the behavior:

1. Trace a LangGraph application (may apply to langchain as well but haven't tested just that) using our LangChainInstrumentor
2. Save traces using the code above
3. (Alternatively, use this file for testing: https://storage.googleapis.com/arize-phoenix-assets/traces/langgraph-demo-traces.parquet)
4. Attempt to load those traces using log_traces() method or one of the phoenix serve flags

Expected behavior
Traces will be loaded into the dashboard and visible.

Environment (please complete the following information):

• OS: MacOS
• Notebook Runtime: VSCode
• Browser: all
• Phoenix Version: 4.36.0

Additional context
If you load traces by passing them into the launch_app() method instead of log_traces, they will be loaded correctly.