Remove the assertion for now.  This breaks lld.

lld has a hashtable with StringRef keys; it needs to iterate over the keys in
*insertion* order.  This is currently implemented as std::vector<StringRef> +
DenseMap<StringRef, T>.  This will probably need a proper
DenseMapInfo<StringRef> if we don't want to lose memory/performance by
migrating to a different data structure.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187868 91177308-0d34-0410-b5e6-96231b3b80d8