Remove unused include from IVFlib.cpp (#4534)

Summary:
Pull Request resolved: #4534

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## Summary:
Remove unused `#include <numeric>` directive from IVFlib.cpp to clean up the code.

Analysis confirmed that no functions from the `<numeric>` header (std::accumulate, std::iota, std::adjacent_difference, std::inner_product, std::partial_sum) are used in this file.

This reduces compilation dependencies and improves build times by removing unnecessary header includes.
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Reviewed By: mnorris11

Differential Revision: D80324209

fbshipit-source-id: a7e5751590680983ea171ac6514bc4525c94bd07

Author: junjieqi

faiss/IVFlib.cpp

@@ -9,7 +9,6 @@
 #include <omp.h>
 
 #include <memory>
-#include <numeric>
 
 #include <faiss/IndexAdditiveQuantizer.h>
 #include <faiss/IndexIVFAdditiveQuantizer.h>