fix

Signed-off-by: Joe Isaacs <joe.isaacs@live.co.uk>

Author: joseph-isaacs

vortex/benches/common_encoding_tree_throughput.rs

@@ -23,7 +23,6 @@ use vortex::array::arrays::TemporalArray;
 use vortex::array::arrays::VarBinArray;
 use vortex::array::arrays::VarBinViewArray;
 use vortex::array::builtins::ArrayBuiltins;
-use vortex::array::vtable::ValidityHelper;
 use vortex::dtype::DType;
 use vortex::dtype::PType;
 use vortex::encodings::alp::alp_encode;