### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

Authorization headers being sent to API gateway are received on lambdas as "empty string"

### Expected Behavior

_No response_

### How are you starting LocalStack?

With a docker-compose file

### Steps To Reproduce

Run a API Gateway with lambda integration

### Environment

```markdown
- OS:
- LocalStack:
```


### Anything else?

_No response_
if region and region.startswith("us-gov-"):
            return "aws-us-gov"
        elif region and region.startswith("us-iso-"):
            return "aws-iso"
        elif region and region.startswith("us-isob-"):
            return "aws-iso-b"
        elif region and region.startswith("cn-"):
            return "aws-cn"
        elif region and re.match(r"^(us|eu|ap|sa|ca|me|af)-\w+-\d+$", region):
            return "aws"
        else:
            raise ArnPartitionRewriteListener.InvalidRegionException(
                f"Region ({region}) could not be matched to a partition."
            )
    @staticmethod
    def _post_process_response_headers(response: RoutingResponse) -> None: