Remove extra semi colon from facer/engine/libsvm/svm.cpp

Summary:
`-Wextra-semi` or `-Wextra-semi-stmt`

If the code compiles, this is safe to land.

Reviewed By: palmje

Differential Revision: D51995074

fbshipit-source-id: 4863250ff9f4b87241f6c01cf3b39b6b87172852

faiss/impl/AdditiveQuantizer.h

@@ -203,4 +203,4 @@ struct AdditiveQuantizer : Quantizer {
     virtual ~AdditiveQuantizer();
 };
 
-}; // namespace faiss
+} // namespace faiss