Remove unused ARGBAttenuateRow_Any_SSE2 prototype

Bug: libyuv:769
Test: try bots build
Change-Id: I9633637cee1dc17bc62dd0598b1ea1edc15cf646
Reviewed-on: https://chromium-review.googlesource.com/847702Reviewed-by: Frank Barchard <fbarchard@chromium.org>
Reviewed-by: Weiyong Yao <braveyao@chromium.org>
Commit-Queue: Frank Barchard <fbarchard@chromium.org>

include/libyuv/row.h

@@ -2755,9 +2755,6 @@ void ARGBAttenuateRow_SSSE3(const uint8* src_argb, uint8* dst_argb, int width);
 void ARGBAttenuateRow_AVX2(const uint8* src_argb, uint8* dst_argb, int width);
 void ARGBAttenuateRow_NEON(const uint8* src_argb, uint8* dst_argb, int width);
 void ARGBAttenuateRow_MSA(const uint8* src_argb, uint8* dst_argb, int width);
-void ARGBAttenuateRow_Any_SSE2(const uint8* src_argb,
-                               uint8* dst_argb,
-                               int width);
 void ARGBAttenuateRow_Any_SSSE3(const uint8* src_argb,
                                 uint8* dst_argb,
                                 int width);