Update tool tip for fax detect

Inbound route, fax tab, Fax Detection type tool tip states:

Type of fax detection to use.
Dahdi: use Dahdi fax detection; requires 'faxdetect=' to be set to 'incoming' or 'both' in Dahdi.conf
Sip: use sip fax detection (t38). Requires asterisk 1.6.2 or greater and 'faxdetect=yes' in the sip config files
NV Fax Detect: Use NV Fax Detection; Requires NV Fax Detect to be installed and recognized by asterisk

Please remove reference to NV Fax, it was removed a long time ago

Type of fax detection to use.
Dahdi: use Dahdi fax detection; requires 'faxdetect=' to be set to 'incoming' or 'both' in Dahdi.conf
Sip: use sip fax detection (t38). Requires asterisk 1.6.2 or greater and 'faxdetect=yes' in the sip config files