CMake/MSVC: Remove stale OIIO sse flag

We disabled SSE for OIIO headers in the days we still supported
32 bit builds, as it was giving build errors there. OIIO handles
this internally now so we no longer need to explicitly disable it,
also we stopped shipping 32 bit quite a while ago

build_files/cmake/platform/platform_win32.cmake

@@ -674,7 +674,6 @@ if(NOT OpenImageIO_FOUND)
   set(OPENIMAGEIO_LIBRARIES ${OIIO_OPTIMIZED} ${OIIO_DEBUG})
   set(OPENIMAGEIO_IDIFF "${OPENIMAGEIO}/bin/idiff.exe")
 endif()
-add_definitions(-DOIIO_NO_SSE=1)
 
 if(WITH_LLVM)
   set(LLVM_ROOT_DIR ${LIBDIR}/llvm CACHE PATH "Path to the LLVM installation")