Remap SIP_REQUEST_CANCELLED DisconnectCause to NORMAL.

This CL prevents dialer from displaying the incorrect pop-up after a call is terminated due to CODE_SIP_REQUEST_CANCELLED. The invalid pop-up "Call terminated due to a problem with the Network"  should not be shown in this case as this should be considered NORMAL call clearing so this CL remaps that disconnect code to DisconnectCause.NORMAL.

Flag: com.android.internal.telephony.flags.remap_disconnect_cause_sip_request_cancelled
Test: ImsPhoneCallTrackerTest#testSipRequestCancelled
Fixes: 351258918
Change-Id: Id15c7ac3969b001daba79af5726107597614acf1