Rename client building function to _build_dummy_client for clarity

[howieleung]

Description

Please add an informative description that covers that changes made by the pull request and link all relevant issues.

If an SDK is being regenerated based on a new API spec, a link to the pull request containing these API spec changes should be included above.

All SDK Contribution checklist:

• The pull request does not introduce [breaking changes]
• CHANGELOG is updated for new features, bug fixes or other significant changes.
• I have read the contribution guidelines.

General Guidelines and Best Practices

• Title of the pull request is clear and informative.
• There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For more information on cleaning up the commits in your PR, see this page.

Testing Guidelines

• Pull request includes test coverage for the included changes.

[Copilot]

Pull request overview

This PR renames a helper function from _build_client to _build_dummy_client in test files to better clarify its purpose. The function creates a test client with dummy credentials for unit testing purposes.

Changes:

• Renamed _build_client function to _build_dummy_client in both synchronous and asynchronous test files
• Updated all call sites to use the new function name

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
sdk/ai/azure-ai-projects/tests/responses/test_responses_async.py	Renamed helper function definition and its single usage in async test
sdk/ai/azure-ai-projects/tests/responses/test_responses.py	Renamed helper function definition and its single usage in sync test

[github-actions]

API Change Check

APIView identified API level changes in this PR and created the following API reviews

azure-ai-projects