Remove confusing comments in partitioning.cpp (facebookresearch#3104)

Summary:
Fix facebookresearch#3095

Pull Request resolved: facebookresearch#3104

Reviewed By: mlomeli1

Differential Revision: D50595865

Pulled By: mdouze

fbshipit-source-id: f9107bda114a77d6e1f0da32c3451b7182d32e60

faiss/utils/partitioning.cpp

@@ -750,8 +750,6 @@ typename C::T partition_fuzzy(
         size_t q_min,
         size_t q_max,
         size_t* q_out) {
-    // the code below compiles and runs without AVX2 but it's slower than
-    // the scalar implementation
 #ifdef __AVX2__
     constexpr bool is_uint16 = std::is_same<typename C::T, uint16_t>::value;
     if (is_uint16 && is_aligned_pointer(vals)) {