[test] Workaround C1XX bug in uses_allocator_types.hpp

VSO#109062 "Explicit template argument specification with empty template parameter pack expansion does not imply further empty pack expansion"

Differential Revision: https://reviews.llvm.org/D33214

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@303888 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed