Remove unused function from faiss/clone_index.cpp

Summary: `-Wunused-function` has identified an unused function. This diff removes it. In many cases these functions have existed for years in an unused state.

Reviewed By: palmje

Differential Revision: D53049728

fbshipit-source-id: b3d6b98e4ef035f257e9120369b0e70b3200bec0

Author: r-barnes

faiss/clone_index.cpp

@@ -238,13 +238,6 @@ Index* clone_AdditiveQuantizerIndex(const Index* index) {
 
 namespace {
 
-IndexHNSW* clone_HNSW(const IndexHNSW* ihnsw) {
-    TRYCLONE(IndexHNSWFlat, ihnsw)
-    TRYCLONE(IndexHNSWPQ, ihnsw)
-    TRYCLONE(IndexHNSWSQ, ihnsw)
-    return new IndexHNSW(*ihnsw);
-}
-
 InvertedLists* clone_InvertedLists(const InvertedLists* invlists) {
     if (auto* ails = dynamic_cast<const ArrayInvertedLists*>(invlists)) {
         return new ArrayInvertedLists(*ails);