obsolete API calls to read user details

[twhelik]

GET prevelcer.herokuapp.com/api/user
GET prevelcer.herokuapp.com/api/user/
gives out the same response body. Only one of them will be needed.

body
{
"username": "Helik",
"first_name": "Helik",
"last_name": "Tribuwan",
"email": "heliktribuwan995@gmail.com"
}