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: I61dce7786ed2c58f226676100ffb17d44a15bc48