Remove `type="email"` from username field in Register

As the username doesn't have to be an email, having email as the type is incorrect.
This change also makes it more consistent with the way it is defined in the login form.

ui/src/user/Register.tsx

@@ -51,7 +51,6 @@ export default class RegistrationDialog extends Component<IProps, IState> {
                         className="name"
                         label="Name *"
                         name="username"
-                        type="email"
                         value={name}
                         onChange={this.handleChange.bind(this, 'name')}
                         fullWidth