Update the string values for the error message while network scan.

Change the error message from "Error while searching for networks."
to "Couldn't find networks. Try again." according to the off-line
discussion with UX writer for Connectivity.

Bug: 72052945, 70530820
Test: Manual test
Change-Id: Ib923e7178de99e2a15b58f02f816485c33abf652
1 file changed