Update COMPONENT for platform/json

Updates COMPONENT for platform/json since Blink>Internals is getting deprecated.
https://docs.google.com/document/d/1aIyRShgMPy1TmuaMK-hI7j6bewbjqc4Nyxp0N0PTvGE/edit

Bug: None
Change-Id: I420d8143ec483f7366efa0fb5ff2197916e62949
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2416152Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Keishi Hattori <keishi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809616}

third_party/blink/renderer/platform/json/OWNERS

 pfeldman@chromium.org
 iclelland@chromium.org
 
-# COMPONENT: Blink>Internals
+# COMPONENT: Blink>Internals>WTF