fixing inconsistent naming from Flask to FastAPI

[cerashdan]

Description

Correcting a typo in the docs as it is inconsistent with the remaining examples.

Type of Change

• Typo/formatting fix in /user-guide/deploy/deploy_to_aws_fargate.md in section "## Creating Your Agent in Python" mentions a Flask application. While the referenced app in /examples/cdk/deploy_to_fargate/docker/app/app.py is using FastAPI library only

Motivation and Context

Typo/formatting

Areas Affected

/user-guide/deploy/deploy_to_aws_fargate.md

Screenshots

This is a single word change from Flask to FastAPI

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
• Images/diagrams are properly sized and formatted
• All new and existing tests pass

Additional Notes

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