Remove friend class that doesn't exist in SafeBrowsingService

SafeBrowsingURLRequestContextGetter doesn't exist anymore, so remove the
friend class declaration.

Bug: 678653
Change-Id: If8e5105ff5e8178f3402372c4df43138e30c1a92
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2041887
Auto-Submit: Daniel Rubery <drubery@chromium.org>
Reviewed-by: Xinghui Lu <xinghuilu@chromium.org>
Commit-Queue: Xinghui Lu <xinghuilu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#739216}

chrome/browser/safe_browsing/safe_browsing_service.h

@@ -210,7 +210,6 @@ class SafeBrowsingService : public SafeBrowsingServiceInterface,
   friend class extensions::SafeBrowsingPrivateApiUnitTest;
   friend class SafeBrowsingServerTest;
   friend class SafeBrowsingUIManagerTest;
-  friend class SafeBrowsingURLRequestContextGetter;
   friend class TestSafeBrowsingService;
   friend class TestSafeBrowsingServiceFactory;
   friend class V4SafeBrowsingServiceTest;