Settings WebUI: Make menu outlines extend the full widths

https://imgur.com/a/8zA9Fxq

Bug: 1048552
Change-Id: I10da9e12e233b4afade004a21a4ee25ba61d1c7b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2112811Reviewed-by: Esmael Elmoslimany <aee@chromium.org>
Commit-Queue: John Lee <johntlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#752198}

chrome/browser/resources/settings/settings_menu/settings_menu.html

@@ -29,6 +29,12 @@
         -webkit-tap-highlight-color: transparent;
       }
 
+      #topMenu {
+        display: flex;
+        flex-direction: column;
+        min-width: fit-content;
+      }
+
       a[href],
       #advancedButton {
         align-items: center;