libnetdutils: avoid deque<const T>

A container of const T uses std::allocator<const T>, which was an
undocumented libc++ extension that has been removed.

See https://github.com/llvm/llvm-project/pull/96319.

Bug: 349681543
Test: m libnetdutils
Change-Id: I0b0eb07a6c95b4781ad04a82068bd33aef68e33b
1 file changed