Remove extra semi colon from faiss/IndexIVFSpectralHash.cpp

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

If the code compiles, this is safe to land.

Reviewed By: algoriddle

Differential Revision: D52968923

fbshipit-source-id: 5754c0b17b46bc90d0f05d66bbfacb24fee5caae

faiss/IndexIVFSpectralHash.cpp

@@ -157,7 +157,7 @@ void binarize_with_freq(
     }
 }
 
-}; // namespace
+} // namespace
 
 void IndexIVFSpectralHash::encode_vectors(
         idx_t n,