remove extra include

a duplicate include messes up msvs sometimes

R=egdaniel@google.com

Bug: skia:
Change-Id: I3f16c4896064e00213aaf640575c694d1c59a462
Reviewed-on: https://skia-review.googlesource.com/c/164603
Commit-Queue: Cary Clark <caryclark@skia.org>
Commit-Queue: Greg Daniel <egdaniel@google.com>
Auto-Submit: Cary Clark <caryclark@skia.org>
Reviewed-by: Greg Daniel <egdaniel@google.com>
diff --git a/gn/gpu.gni b/gn/gpu.gni
index 3c33b26..7f91ffa 100644
--- a/gn/gpu.gni
+++ b/gn/gpu.gni
@@ -249,7 +249,6 @@
   "$_src/gpu/ops/GrDashLinePathRenderer.h",
   "$_src/gpu/ops/GrDashOp.cpp",
   "$_src/gpu/ops/GrDashOp.h",
-  "$_src/gpu/ops/GrDebugMarkerOp.h",
   "$_src/gpu/ops/GrDefaultPathRenderer.cpp",
   "$_src/gpu/ops/GrDefaultPathRenderer.h",
   "$_src/gpu/ops/GrDebugMarkerOp.cpp",