[libc++] Revert "Make `vector` unconditionally move elements when exceptions are disabled."

This reverts r370502, which broke the use case of a copy-only T (with a
deleted move constructor) when exceptions are disabled. Until we figure
out the right behavior, I'm reverting the commit.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@371068 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed