Remove unusual static method call

The code is using static method Calendar.getInstance() but via a
subclass of Calendar. It works, and getInstance() returns a
GregorianCalendar on Android, but it's odd and was probably unintended.

Noticed during static analysis of SystemUI bytecode.

Bug: 111055375
Test: build / boot
Change-Id: I1762cbeb2cc7882868f84ec11100815671cd29ec