Move Java9LanguageFeaturesTest.java into correct directory.

The path accidentally didn't quite match the package name (with its
repeated libcore), which violates the convention, and causes issues
for some tools (e.g. vogar considers it an error).

Test: cts-tradefed run cts-dev -m CtsLibcoreTestCase -t libcore.libcore.internal
Change-Id: Iadd4ac5a28ca9041514804d672dc480f96824213
2 files changed