Dialer: do not assume which subscription to use in call detail header

This subscription is the last one used to make a call, and it is being
forwarded to the call intent. Let the receiver handle the logic of
picking which SIM (or whether to prompt) to use.

Change-Id: Ibed0b0b8faabb7ac20cc590a3dd327269b71b4f4
Signed-off-by: Roman Birg <roman@cyngn.com>