Remove obsolete comment from renderer_webcookiejar_impl.h.

In the intervening almost-nine years, we have managed to add this #include.

Change-Id: I68673f7c0f6e83fd604e8d227062acd179a18a9e
Reviewed-on: https://chromium-review.googlesource.com/c/1330210Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Jeremy Roman <jbroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607229}

content/renderer/renderer_webcookiejar_impl.h

@@ -5,7 +5,6 @@
 #ifndef CONTENT_RENDERER_RENDERER_WEBCOOKIEJAR_IMPL_H_
 #define CONTENT_RENDERER_RENDERER_WEBCOOKIEJAR_IMPL_H_
 
-// TODO(darin): WebCookieJar.h is missing a WebString.h include!
 #include "third_party/blink/public/platform/web_cookie_jar.h"
 
 namespace content {