Replace clearCachedDefault with setICUDefault

- New method setICUDefault from upstream ICU starting from 60
  can clear the default timezone. It has the same effect as method
  clearCachedDefault in Android.
- In favour of the new method from upstream,
  the local patch http://r.android.com/233357
  has been removed in Android.

Bug: 30938145
Test: cts-tradefed run cts -m CtsLibcoreTestCases --test
libcore.java.util.TimeZoneTest
Change-Id: I288ce425de626a6bc96a8b4a88adec1b5ffb6d05
2 files changed