Fixed phone number not seen on about page

Made format phone number utility method case insensitive.

Fix: 271753491
Test: Verified on settings->about->phone number
Test: atest android.telephony.cts.PhoneNumberUtilsTest
Test: atest com.android.internal.telephony.PhoneNumberUtilsTest
Change-Id: Ib0410755ec650b2ca286009f4161d6c888c9642a