Top line should show "Primary data" for users with > 1 plans.

When the platform receives data plan information and the
user has more than one data plans, the top line under
Settings -> Network & Internet -> Data Usage should read
"Primary data" instead of "Current data".

Bug: 77295381

Test: manual
Test: make RunSettingsRoboTests
Change-Id: Ia9d9d04919c28b163979c70f91eb7d72cdebcb89