res_pjsip_nat.c: remove x-ast-orig-host from request URI and To header

res_pjsip_nat.c: remove x-ast-orig-host from request URI and To header

While asterisk is filtering out the x-ast-orig-host parameter from the
contact on response messages, it is not filtering it out from the
request URI and the to header on SIP requests (for example INVITE).

ASTERISK-28884 #close

Change-Id: Id032b33098a1befea9b243ca994184baecccc59e