Remove unused headers from AutoTune.cpp and clone_index.cpp (#4513)

Summary:

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## Summary:

This diff removes unused headers from two faiss files:

**AutoTune.cpp:**
- Removed unused `#include <cmath>` header
- Analysis confirmed no mathematical functions (sqrt, pow, ceil, etc.) are used in the file

**clone_index.cpp:**
- Removed unused `#include <cstdio>` header (no printf/fprintf calls)
- Removed unused `#include <cstdlib>` header (no abort/exit/malloc calls)
- Kept `#include <faiss/impl/FaissAssert.h>` which is used extensively

These changes reduce compilation overhead and dependencies without affecting functionality.
---
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Differential Revision: D79785715

Author: Racer Engineer

faiss/AutoTune.cpp

@@ -14,7 +14,6 @@
 #include <faiss/AutoTune.h>
 
 #include <cinttypes>
-#include <cmath>
 
 #include <faiss/impl/FaissAssert.h>
 #include <faiss/utils/random.h>

faiss/clone_index.cpp

@@ -9,9 +9,6 @@
 
 #include <faiss/clone_index.h>
 
-#include <cstdio>
-#include <cstdlib>
-
 #include <faiss/impl/FaissAssert.h>
 
 #include <faiss/Index2Layer.h>