system-web-apps: Remove out of date comment.

The browser test no longer requires us to update it every time we add
a new app.

Change-Id: If6e932b72fd03184ae901b69f8129edf44421fb7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2383403
Commit-Queue: Jiewei Qian  <qjw@chromium.org>
Auto-Submit: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Reviewed-by: Jiewei Qian  <qjw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#803025}

chrome/browser/web_applications/system_web_app_manager.h

@@ -59,9 +59,6 @@ enum class SystemAppType {
   TELEMETRY,
   SAMPLE,
 #endif  // !defined(OFFICIAL_BUILD)
-
-  // When adding a new system app, update system_web_app_manager_browsertest.cc
-  // |GetExpectedNumberOfInstalledSystemApps| method accordingly.
 };
 
 using OriginTrialsMap = std::map<url::Origin, std::vector<std::string>>;