Polish on mobile network settings

Update some strings:
In settings it has the same resId for this title so I skipped migration
for it. Actually it should be "Access Point Names" instead of "APNs".
Also since "roaming" is used nowhere so we can update the string
directly.

Also remove unused files

Bug: 114749736
Test: Manual
Change-Id: Ia2f8a352865b9577e0385045f1ad2604ab2bb6af
4 files changed