Fix incorrect examples for to_file() and memory_exporter usage

[moufuyu]

Description

There are two corrections:

In the usage example for Trace-based Helpfulness Evaluation, the following code appears:

# Setup telemetry for trace capture
telemetry = StrandsEvalsTelemetry().setup_in_memory_exporter()

def user_task_function(case: Case) -> dict:
    # Clear previous traces
    telemetry.memory_exporter.clear()

However, the correct property name is in_memory_exporter, not memory_exporter.

Fixed the usage of to_file()in the sections Basic Output Evaluation, Tool Usage Evaluation, and Automated Experiment Generation to match the correct method signature.

Related Issues

Type of Change

Typo/formatting fix

Checklist

• I have read the CONTRIBUTING document
• My changes follow the project's documentation style
• I have tested the documentation locally using mkdocs serve
• Links in the documentation are valid and working

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