Wrong type for unique_key_policy in CosmosDB async DatabaseProxy.create_container

- **Package Name**: azure-cosmos
- **Package Version**: 4.9.0
- **Operating System**: mcr.microsoft.com/devcontainers/python:1-3.13 through WSL
- **Python Version**: 3.13

**Describe the bug**
For the `DatabaseProxy.create_container` method, `unique_key_policy` should be typed as `Dict[str, Any] | None` as in the sync counterpart.

It's now `Dict[str, str] | None` for async.

**To Reproduce**
Steps to reproduce the behavior:
1. Install the package

**Expected behavior**
unique_key_policy should be typed as `Dict[str, Any] | None` as in the sync counterpart.

**Screenshots**
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**Additional context**
Add any other context about the problem here.

Compare the async DatabaseProxy.create_container annotation for unique_key_policy with the sync counterpart mentioned in the issue. Confirm the async signature accepts Dict[str, Any] | None, then run the relevant azure-cosmos tests or type checks to verify the corrected annotation.

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