(stepfunctions-tasks): Regression in AthenaStartQueryExecution

#11203 introduced a small regression wherein you can no longer use a JSON Path to specify properties for a `StartQueryExecution` AWS service call.

Specifically, `outputLocation` was changed from a string to this:

https://github.com/aws/aws-cdk/blob/f26a592e609674d528990aad14fb8884112ad64d/packages/%40aws-cdk/aws-stepfunctions-tasks/lib/athena/start-query-execution.ts#L239

Which means that this example in the README no longer compiles - and the functionality it represents does not appear to be possible any longer.

https://github.com/aws/aws-cdk/blob/f26a592e609674d528990aad14fb8884112ad64d/packages/%40aws-cdk/aws-stepfunctions-tasks/README.md#L235

Start in packages/@aws-cdk/aws-stepfunctions-tasks/lib/athena/start-query-execution.ts around the outputLocation definition, then compare it with the JSONPath example in packages/@aws-cdk/aws-stepfunctions-tasks/README.md. Confirm how the regression prevents that example from compiling and restore support so the documented StartQueryExecution JSONPath usage compiles again.

Written by the indexing model from the issue text.