SunOS: Remove obsolete Studio compiler library directories

Our CMAKE_PLATFORM_IMPLICIT_LINK_DIRECTORIES setting is no longer needed
because CMAKE_<LANG>_IMPLICIT_LINK_DIRECTORIES is now populated with the
actual implicit link directories for the current toolchain.  The old
values we hard-coded in CMAKE_PLATFORM_IMPLICIT_LINK_DIRECTORIES are not
relevant to modern toolchains, so simply drop them.

Co-Author: Shawn Walker-Salas <shawn.walker@oracle.com>