Response to delete should be 204 No Content

[Kevsy]

Problem description

The current response to deleting a session is 200 OK, but it should be 204 No Content

Expected behavior

Change the delete response for /sessions/{sessionId} to 204 No Content

Alternative solution

Additional context

[XunliYang]

Thanks for pointing out. This makes sense and has already been revised in the PR #59 and in the commit Modify error codes usage with appropriate error codes.