remove SK_DISABLE_LOWP_BILERP_CLAMP_CLAMP_STAGE

It does nothing.

Change-Id: I9f170d43a18fe5e07032fd1f4a8e093a65992ee4
Reviewed-on: https://chromium-review.googlesource.com/1106003Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568522}

skia/config/SkUserConfig.h

@@ -184,9 +184,6 @@ SK_API void SkDebugf_FileLine(const char* file, int line, bool fatal,
 // Remove this and rebaseline affected layout tests.
 #define SK_DONT_DROP_UNNECESSARY_AA_IN_TEXTURE_OP
 
-#define SK_DISABLE_LOWP_BILERP_CLAMP_CLAMP_STAGE
-
-
 #ifndef SK_SUPPORT_LEGACY_THREADED_DAA_BUGS
 #define SK_SUPPORT_LEGACY_THREADED_DAA_BUGS
 #endif