apns: Remove proxy for the "TIM WAP" APN

The proxy prevents mobile data from working
(e.g. loading a webpage results in ERR_EMPTY_RESPONSE).

On all the mobile phones I've inserted the SIM in,
when the APN's are obtained automatically
this parameter is not set to any value.

Also remove unnecessary parameters and correct authentication type.

Change-Id: I16592de4555fb8ab3fe502b3b39779720c344afb