removeAttribute 
  Removes an attribute.
Return
The AttributeEditor.
Parameters
attribute
The attribute. Must be greater must be greater than 1 character and not contain #.
Throws
if:
- The key is empty or contains - #.
fun removeAttribute(@Size(min = 1)  attribute: String, @Size(min = 1)  instanceId: String): AttributeEditor
Removes a JSON attribute for the given instance.
Return
The AttributeEditor.
Parameters
attribute
The attribute.
instanceId 
The instance identifier.
Throws
if:
- The key is empty or contains - #.