Remove test for unsupported GregorianCalendar functionality.

Also adds an explanatory comment and makes the
intent of the implementation clearer without changing
any of the functionality.

TL;DR - there doesn't appear to be any sensible way
to provide any sort of consisent semantics if we plan
on supporting these fields.

bug: 12778197

Change-Id: Iadaaaa5d4bdddec4aceca498ffc870edf2cbefed
2 files changed