Remove bad third_party/skia file.

This file should not exist and causes issues with gclient.
diff --git a/third_party/skia b/third_party/skia
deleted file mode 160000
index ed854fb..0000000
--- a/third_party/skia
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit ed854fb897fa134f2f64738a75293502fdcf1af2