Update openai requirement from ~=1.54.4 to ~=1.57.4 in /code/backend

Updates the requirements on [openai](https://github.com/openai/openai-python) to permit the latest version.
- [Release notes](https://github.com/openai/openai-python/releases)
- [Changelog](https://github.com/openai/openai-python/blob/main/CHANGELOG.md)
- [Commits](openai/openai-python@v1.54.4...v1.57.4)

---
updated-dependencies:
- dependency-name: openai
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

code/backend/requirements.txt

@@ -5,7 +5,7 @@ botbuilder-core~=4.16.2
 botbuilder-azure~=4.16.2
 botbuilder-integration-aiohttp~=4.16.2
 botbuilder-dialogs~=4.16.2
-openai~=1.54.4
+openai~=1.57.4
 opentelemetry-instrumentation-aiohttp-client~=0.49b2
 opentelemetry-instrumentation-aiohttp-server~=0.49b2
 pydantic~=2.9.2