Revert "put kNone back too"

This reverts commit 49e1239f94.

Reason for revert: need more

Original change's description:
> put kNone back too
> 
> Change-Id: I07969ca6b7367460259901cf526b11cbf2793663
> Reviewed-on: https://skia-review.googlesource.com/c/170420
> Auto-Submit: Mike Klein <mtklein@google.com>
> Reviewed-by: Mike Klein <mtklein@google.com>
> Commit-Queue: Mike Klein <mtklein@google.com>

TBR=mtklein@google.com,reed@google.com

Change-Id: Id027f6d82d2c61bfc6a2c4ee4f894452830e6889
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/170421
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>

include/codec/SkCodec.h

@@ -594,11 +594,6 @@ public:
     //   is residing in dst's memory.
     static constexpr int kNoFrame = -1;
 
-    // This transitional definition was added in August 2018, and will eventually be removed.
-#ifdef SK_LEGACY_SKCODEC_NONE_ENUM
-    static constexpr int kNone = kNoFrame;
-#endif
-
     /**
      *  Information about individual frames in a multi-framed image.
      */