Update and refine sample description about using Azure Logic Apps with agents in Foundry

[ecfan]

Updated descriptions and prerequisites for Azure Logic Apps terminology, casing, clarity, and consistency with Microsoft writing style.

Description

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[Copilot]

Pull request overview

Updates the introductory docstring of the sample_agents_logic_apps.py sample to improve Azure Logic Apps/Foundry terminology, prerequisites, and setup guidance for running the sample.

Changes:

• Refines the sample description to explicitly reference Azure Logic Apps and clarify the scenario.
• Rewrites prerequisites/setup text (Logic Apps resource type, HTTP Request trigger, and updated Learn link).
• Updates environment variable guidance language and formatting.