[bugfix] Dispose helper when removing it

[vincentfretin]

Dispose helper when removing it to properly dispose material and geometry.
In recent three.js version all helpers have now a dispose function, that was not the case historically.
This is similar to three.js editor
https://github.com/mrdoob/three.js/blob/267e76c2d884cb0b4c12f4c5ffa5a7d03ce82bba/editor/js/Editor.js#L472

Also remove the second argument to CameraHelper, CameraHelper only takes one argument.
https://github.com/mrdoob/three.js/blob/267e76c2d884cb0b4c12f4c5ffa5a7d03ce82bba/src/helpers/CameraHelper.js#L21

[dmarcos]

Thank you!