[libc++] Disable <chrono> ""d and ""y literal tests on AppleClang 10.0.0

In r368882, I enabled those tests for all AppleClang's above version 9.
However, it turns out that the feature is only supported starting with
AppleClang 10.0.1, not AppleClang 10.0.0. This commit fixes that hole.

llvm-svn: 369409