Remove SkUnitMappers from skia_gn_files.gypi

No longer used/present.

R=reed@google.com

Review URL: https://codereview.chromium.org/298973006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@272306 0039d316-1c4b-4281-b951-d872f2087c98

skia/skia_gn_files.gypi

@@ -103,7 +103,6 @@
     '<(skia_src_path)/utils/SkThreadUtils_win.h',
     '<(skia_src_path)/utils/SkTFitsIn.h',
     '<(skia_src_path)/utils/SkTLogic.h',
-    '<(skia_src_path)/utils/SkUnitMappers.cpp',
 
     #mac
     '<(skia_include_path)/utils/mac/SkCGUtils.h',