Revert patches for the new SystemClock.instant() implementation

Increase the precision of the implementation of java.time.Clock.systemUTC()

See the following links in upstream for details:
https://bugs.openjdk.java.net/browse/JDK-8068730
https://github.com/openjdk/jdk11u/commit/b5f5424c83e28240a3eb280251ffe604a294ac20

Bug: 180577079
Test: TestClock_System
Change-Id: Ic4d6843d6bd7f67bb5d6660917e4f4cf3fe41240
2 files changed