Remove duplicate partial specialization.

Author: kevyuu

include/nbl/builtin/hlsl/type_traits.hlsl

@@ -855,9 +855,6 @@ struct float_of_size<8>
 template<uint16_t bytesize>
 using float_of_size_t = typename float_of_size<bytesize>::type;
 
-template<typename T, int N>
-struct extent<vector<T, N>, 0> : integral_constant<uint64_t, N> {};
-
 template<typename T, int N, int M>
 struct extent<matrix<T, N, M>, 0> : integral_constant<uint64_t, N> {};