Remove outdated comment from content_settings_client.h

components/content_settings/core/browser/content_settings_client.h

Index: components/content_settings/core/browser/content_settings_client.h
diff --git a/components/content_settings/core/browser/content_settings_client.h b/components/content_settings/core/browser/content_settings_client.h
index 0b89b169d297175a824890c7909c45611d1d1cf6..e6f4a4e0109b8507567866933f178c503568487b 100644
--- a/components/content_settings/core/browser/content_settings_client.h
+++ b/components/content_settings/core/browser/content_settings_client.h
@@ -21,9 +21,6 @@ class CookieOptions;
 namespace content_settings {
 
 // An abstraction of operations that depend on the embedder (e.g. Chrome).
-// For mock / testing implementation in tests you can inherit from
-// StubContentSettingsClient instead to avoid the need to stub unneeded pure
-// virtual methods.
 class ContentSettingsClient {
  public:
   enum AccessType { BLOCKED, ALLOWED };