InCallService: Telephony and Telecom cannot be null

Acknowledge that the BluetoothInCallService cannot be created if there
is no TelephonyManager or TelecomManager

+ cleanup dead code related to variable not being nullable anymore

Bug: 330247213
Test: atest BluetoothInstrumentationTests:BluetoothInCallServiceTest
Flag: Exempt refactor
Change-Id: Ic576c05ff8cbb1dacce56b6ed24e710fd0e9c4ef