Change component to Internals>Images>Codecs

Since third_party/libavif is only used by
third_party/blink/renderer/platform/image-decoders, it makes more sense
for third_party/libavif to be in the same component as
third_party/blink/renderer/platform/image-decoders.

Change-Id: I92c464f662065267311c412e18279e76086ac364
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2302941Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Wan-Teh Chang <wtc@google.com>
Cr-Commit-Position: refs/heads/master@{#789539}

third_party/libavif/OWNERS

-# COMPONENT: Internals>Media>Codecs
+# COMPONENT: Internals>Images>Codecs
 file://media/OWNERS
 wtc@google.com