Change capture for inner lambda

Capture by reference is working on my workstation, but fails on Summit
with
arborx/src/details/ArborX_DetailsTreeTraversal.hpp:102:7: internal compiler error: in maybe_undo_parenthesized_ref, at cp/semantics.c:1739
                                  if (i < real_predicates_in_team) {

This is reminiscent of kokkos/kokkos-kernels#349.

src/details/ArborX_DetailsTreeTraversal.hpp

@@ -98,7 +98,7 @@ struct TreeTraversal<BVH, Predicates, Callback, SpatialPredicateTag>
               real_predicates_end - real_predicates_begin;
 
           Kokkos::parallel_for(Kokkos::TeamThreadRange(team_member, team_size),
-                               [&](int const i) {
+                               [=](int const i) {
                                  if (i < real_predicates_in_team)
                                    tree_traversal(real_predicates_begin + i);
                                });