Remove SkDDLTmpRedirect.h

With the Chrome-side CL:

https://chromium-review.googlesource.com/c/chromium/src/+/2067805 (Switch SkDDLTmpRedirect.h reference to SkDeferredDisplayList.h)

having landed, Skia no longer needs this temporary header.

TBR=bsalomon@google.com
Change-Id: I01da4ece2be239407e223105781d4d0d75deabdb
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/273018
Reviewed-by: Robert Phillips <robertphillips@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>

Author: rphilli

gn/core.gni

@@ -460,7 +460,6 @@ skia_core_sources = [
   # private
   "$_include/private/SkChecksum.h",
   "$_include/private/SkColorData.h",
-  "$_include/private/SkDDLTmpRedirect.h",
   "$_include/private/SkDeque.h",
   "$_include/private/SkFixed.h",
   "$_include/private/SkFloatBits.h",