Update permission requirements for TelecomManager#getLine1Number

To move READ_PHONE_STATE from a runtime permission to a normal
permission all sensitive APIs guarded by READ_PHONE_STATE must be
moved to another permission. This commit updates the TelecomManager
getLine1Number docs to reflect the new permission requirements;
these requirements are the same as TelephonyManager getLine1Number.

Bug: 136160623
Test: atest TelecomUnitTests:TelecomServiceImplTest
Change-Id: Ibb8e5d1cf16a05e95c2cc2fb68af35dc4bdb0f02