[promptflow][bugfix] Fix breaking test due to LineRun.evaluations c…

…ontract change (#2177)

# Description

For `LineRun.evaluations`, it will be a dict for now, update the
corresponding test; need to improve coverage on this.

# All Promptflow Contribution checklist:
- [x] **The pull request does not introduce [breaking changes].**
- [ ] **CHANGELOG is updated for new features, bug fixes or other
significant changes.**
- [x] **I have read the [contribution guidelines](../CONTRIBUTING.md).**
- [ ] **Create an issue and link to the pull request to get dedicated
review from promptflow team. Learn more: [suggested
workflow](../CONTRIBUTING.md#suggested-workflow).**

## General Guidelines and Best Practices
- [x] Title of the pull request is clear and informative.
- [x] 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
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### Testing Guidelines
- [x] Pull request includes test coverage for the included changes.

src/promptflow/tests/sdk_cli_test/e2etests/test_experiment.py

@@ -123,7 +123,7 @@ def test_experiment_start(self):
             assert len(line_runs) == 3
             line_run = line_runs[0]
             assert len(line_run.evaluations) == 1, "line run evaluation not exists!"
-            assert "eval_classification_accuracy" == line_run.evaluations[0].display_name
+            assert "eval_classification_accuracy" == list(line_run.evaluations.values())[0].display_name
 
         # Test experiment restart
         exp = client._experiments.start(exp.name)
@@ -255,7 +255,7 @@ def _assert_result(result):
                 assert len(line_runs) == 1
                 line_run = line_runs[0]
                 assert len(line_run.evaluations) == 1, "line run evaluation not exists!"
-                assert "eval_classification_accuracy" == line_run.evaluations[0].display_name
+                assert "eval_classification_accuracy" == list(line_run.evaluations.values())[0].display_name
             # Test with default data and custom path
             expected_output_path = Path(tempfile.gettempdir()) / ".promptflow/my_custom"
             result = client.flows.test(target_flow_path, experiment=template_path, output_path=expected_output_path)