Renderer Clipboard: Remove gfx::PNGCodec exception.

As a follow-up to https://crrev.com/c/1827244, remove the exception to allow
ui/gfx/codec use in DataTransfer, as there are no longer any uses of
gfx::PNGCodec in the renderer clipboard.

Change-Id: Ic5ee757b24c0c881e8c978255096b1daf0c1f4ae
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1827651Reviewed-by: Darwin Huang <huangdarwin@chromium.org>
Reviewed-by: Michael Wasserman <msw@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Auto-Submit: Darwin Huang <huangdarwin@chromium.org>
Commit-Queue: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#700908}

third_party/blink/tools/blinkpy/presubmit/audit_non_blink_usage.py

@@ -460,7 +460,7 @@ _CONFIG = [
     },
     {
         'paths': ['third_party/blink/renderer/core/clipboard'],
-        'allowed': ['gfx::PNGCodec', 'net::EscapeForHTML'],
+        'allowed': ['net::EscapeForHTML'],
     },
     {
         'paths': ['third_party/blink/renderer/core/css'],