Remove reference to empty file SkUtilsArm.cpp

https://github.com/google/skia/blob/876b045881a6b53d0db19ed812abd8814d7c359c/src/core/SkUtilsArm.cpp
is an empty file.

Change-Id: I6e02cb381a50bf10e0e627712b6af7f701d506f5
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/103530
Reviewed-by: Nigi <nigi@chromium.org>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
Auto-Submit: Kevin Lubick <kjlubick@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
diff --git a/skia/BUILD.gn b/skia/BUILD.gn
index d02f3ba..ea1439b 100644
--- a/skia/BUILD.gn
+++ b/skia/BUILD.gn
@@ -200,10 +200,6 @@
   # This and skia_opts are really the same conceptual target so share headers.
   allow_circular_includes_from = [ ":skia_opts" ]
 
-  if (current_cpu == "arm") {
-    sources += [ "//third_party/skia/src/core/SkUtilsArm.cpp" ]
-  }
-
   # GPU
   if (skia_support_gpu) {
     sources += skia_gpu_public