Fix AppListTestBase comment typo

The "5" became "4" in
https://codereview.chromium.org/1497193002/patch/60001/70050

Change-Id: I8be0f9580cf6262b5dcd8443d46a9e30d94cc8f0
Reviewed-on: https://chromium-review.googlesource.com/c/1491746Reviewed-by: calamity <calamity@chromium.org>
Commit-Queue: Nigel Tao <nigeltao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#636342}

chrome/browser/ui/app_list/app_list_test_util.cc

@@ -25,7 +25,7 @@ void AppListTestBase::SetUp() {
   extensions::ExtensionServiceTestBase::SetUp();
 
   // Load "app_list" extensions test profile.
-  // The test profile has 5 extensions:
+  // The test profile has 4 extensions:
   // - 1 dummy extension (which should not be visible in the launcher)
   // - 2 packaged extension apps
   // - 1 hosted extension app