[python] add test case

[msyyc]

GOAL:

• add test case in /workspaces/typespec/packages/http-client-python/generator/test/generic_mock_api_tests/test_specs_documentation.py and /workspaces/typespec/packages/http-client-python/generator/test/generic_mock_api_tests/asynctests/test_specs_documentation_async.py for [http-specs] Fix bulletPointsModel API signature to match runtime behavior #9200 which fixed a case then we could test it.
• add test case in /workspaces/typespec/packages/http-client-python/generator/test/azure/mock_api_tests and /workspaces/typespec/packages/http-client-python/generator/test/unbranded/mock_api_tests for https://github.com/microsoft/typespec/pull/9259/files which added a new case

NOTE:

• DO add changelog
• DO format your changed files before commit