system-web-app: remove unused header in system_web_app_ui_utils

This is a cleanup after BMO launch. SWA no longer uses extension related
components.

Bug: 1065748
Change-Id: I96e631a1ce5372bed458a4ff2010140950ae70c1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2485356
Auto-Submit: Jiewei Qian  <qjw@chromium.org>
Commit-Queue: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Reviewed-by: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#819266}

chrome/browser/ui/web_applications/system_web_app_ui_utils.cc

@@ -25,7 +25,6 @@
 #include "chrome/browser/ui/browser_navigator.h"
 #include "chrome/browser/ui/browser_navigator_params.h"
 #include "chrome/browser/ui/browser_window.h"
-#include "chrome/browser/ui/extensions/application_launch.h"
 #include "chrome/browser/ui/web_applications/app_browser_controller.h"
 #include "chrome/browser/ui/web_applications/web_app_launch_manager.h"
 #include "chrome/browser/web_applications/components/app_registrar.h"