fix: treat TaskAdherence tool definitions as optional

[slister1001]

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 pull request fixes a bug in the TaskAdherenceEvaluator where the tool_definitions parameter was being treated as required, causing evaluations with only query/response inputs to fail with "Either 'conversation' or individual inputs must be provided." The fix makes tool_definitions an optional parameter by adding it to the _OPTIONAL_PARAMS list.

• Treat tool_definitions as optional in TaskAdherenceEvaluator to allow evaluations without tool-related inputs
• Bump version from 1.13.4 to 1.13.5 for the bug fix release
• Add changelog entry documenting the bug fix

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
sdk/evaluation/azure-ai-evaluation/azure/ai/evaluation/_version.py	Version bump from 1.13.4 to 1.13.5
sdk/evaluation/azure-ai-evaluation/azure/ai/evaluation/_evaluators/_task_adherence/_task_adherence.py	Added tool_definitions to _OPTIONAL_PARAMS list to make it optional
sdk/evaluation/azure-ai-evaluation/CHANGELOG.md	Added changelog entry for version 1.13.5 documenting the bug fix

[slister1001]

/check-enforcer override