HeadsetService: temporarily skip MODIFY_PHONE_STATE

This have to be reverted in a short frame and is only intended to
prevent a lot of early user breakage
Note that this permission is still enforce for any method starting of
stopping sco.

Test: None
Flag: Exempt, need immediat usage for Android Automotive
Bug: 356478621
Change-Id: Ia984c44c8719d310766955d7fc41d7765c03d26b