[libcxx] [test] Fix the get/put long_double_ru_RU tests on Apple platforms

This fixes issue #45084 (https://llvm.org/PR45739).

Remove unnecessary trailing spaces after the "RUB" international
currency symbol (and after the plain number in some parts of the
put_long_double test).

Both of these test files are
`XFAIL: netbsd || linux || LIBCXX-WINDOWS-FIXME`, and then have some of
their test cases commented out when `__APPLE__`. This patch comments-in
those test cases and adjusts them all to work on Apple, while leaving the
test `XFAIL`ed on NetBSD, Linux, and Windows.

Differential Revision: https://reviews.llvm.org/D120316