refactor(durable): Remove time scale configuration from emulator container

[ayushiahjolia]

Which issue(s) does this change fix?

Related to aws/aws-durable-execution-sdk-python#523

Why is this change necessary?

The time scale feature has been removed from the durable execution emulator (see linked SDK PR). The DURABLE_EXECUTIONS_TIME_SCALE environment variable and the DURABLE_EXECUTION_TIME_SCALE container environment variable are no longer recognized by the emulator, so SAM CLI should stop setting them.

How does it address the issue?

• Removes the ENV_TIME_SCALE class variable and its docstring
• Removes the _get_emulator_time_scale() method
• Updates _get_emulator_environment() to return an empty dict
• Updates unit tests to remove time scale assertions and the custom_time_scale test case

What side effects does this change have?

Users who previously set DURABLE_EXECUTIONS_TIME_SCALE will no longer see it forwarded to the emulator container. Since the emulator itself no longer supports this variable, there is no functional impact.

Mandatory Checklist

PRs will only be reviewed after checklist is complete

• Review the generative AI contribution guidelines
• Add input/output type hints to new functions/methods
• Write design document if needed (Do I need to write a design document?)
• Write/update unit tests
• Write/update integration tests
• Write/update functional tests if needed
• make pr passes
• make update-reproducible-reqs if dependencies were changed
• Write documentation

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.