Clear capture_message_content env var in programmatic override test

[Copilot]

test_can_override_capture_message_content_programmatically was non-deterministic: if OTEL_INSTRUMENTATION_GENAI_CAPTURE_MESSAGE_CONTENT was set in the environment, it would override the programmatic capture_message_content=True argument, causing the assertion to fail or pass for the wrong reason.

Changes

• tests/test_instrumentor.py: Pop OTEL_INSTRUMENTATION_GENAI_CAPTURE_MESSAGE_CONTENT from the environment before calling instrumentor.instrument(capture_message_content=True), ensuring the test actually validates the programmatic override path regardless of CI/local environment state.

def test_can_override_capture_message_content_programmatically(instrument):
    instrument.uninstrument()
    instrumentor = OpenAIInstrumentor()
    env_var = "OTEL_INSTRUMENTATION_GENAI_CAPTURE_MESSAGE_CONTENT"
    os.environ.pop(env_var, None)  # prevent env from overriding programmatic setting
    instrumentor.instrument(capture_message_content=True)
    assert instrumentor.capture_message_content
    instrumentor.uninstrument()