Update COMPONENT for public/mojom/leak_detector

Updates COMPONENT for public/mojom/leak_detector since Blink>Internals is getting deprecated.

https: //docs.google.com/document/d/14CcSzzy_Q0_mg-E9WZKESobpoR66JoWlaJhHzQZKSFA/preview
Bug: None
Change-Id: Ia4a3e6de4eda42637542494d8147262cc002d944
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2417774
Commit-Queue: Keishi Hattori <keishi@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Johann Koenig <johannkoenig@google.com>
Cr-Commit-Position: refs/heads/master@{#808288}

third_party/blink/public/mojom/leak_detector/OWNERS

-# COMPONENT: Blink>Internals
+# COMPONENT: Blink>MemoryAllocator
 
 per-file *.mojom=set noparent
 per-file *.mojom=file://ipc/SECURITY_OWNERS