Deleting user membership uses DELETE with body

### Expected Behavior

As clarified by [RFC 9110](https://www.rfc-editor.org/rfc/rfc9110.html#name-delete) using method body in DELETE requests is not interoperable.

> Although request message framing is independent of the method used, content received in a DELETE request has no generally defined semantics, cannot alter the meaning or target of the request, and might lead some implementations to reject the request and close the connection because of its potential as a request smuggling attack

Deleting user membership should be done by specifying the username as url parameter.

### Dependency-Track Version

4.13.1

### Dependency-Track Distribution

Container Image

### Database Server

PostgreSQL

### Database Server Version

_No response_

### Browser

N/A

### Checklist

- [x] I have read and understand the [contributing guidelines](https://github.com/DependencyTrack/dependency-track/blob/master/CONTRIBUTING.md#filing-issues)
- [x] I have checked the [existing issues](https://github.com/DependencyTrack/dependency-track/issues) for whether this defect was already reported