[Settings] WEA title wording change

The wording of WEA need to align in UI entry and UIs within.
The "Wireless Emergency Alerts" should be the official wording for it.

Bug: 158498436
Test: build pass
Merged-In: I17e6659915e1038c8ab11ad4003c08f87bbdb82e
Change-Id: I4c1c4009287092703669f89981fd017ce605d4fe