Update Monorail component location for CDP

The location for CDP-related bugs is
https://bugs.chromium.org/p/chromium/issues/list?q=component%3APlatform%3EDevTools%3EPlatform&can=2
Moving these bugs from Platform>DevTools to Platform>DevTools>Platform
allows us to separate issues regarding the frontend from issues
regarding the protocol. This also allows us to move issues on other
repositories (like https://github.com/ChromeDevTools/debugger-protocol-viewer/issues into the Monorail component)

Change-Id: I845c2a6ed0eb28925ee7bd15b959b3e75a9a1c67
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2139811Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Tim van der Lippe <tvanderlippe@chromium.org>
Cr-Commit-Position: refs/heads/master@{#757783}

third_party/blink/public/devtools_protocol/OWNERS

@@ -3,4 +3,4 @@ caseq@chromium.org
 dgozman@chromium.org
 pfeldman@chromium.org
 
-# COMPONENT: Platform>DevTools
+# COMPONENT: Platform>DevTools>Platform