Settings: Improve a11y focus indicator on "Advanced" toggle

Fixed: 1081827
Change-Id: Icb6c244bb9f3c01e4848d66c7ed412657065da92
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2378137Reviewed-by: John Lee <johntlee@chromium.org>
Commit-Queue: John Lee <johntlee@chromium.org>
Auto-Submit: dpapad <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801986}

chrome/browser/resources/settings/basic_page/basic_page.html

@@ -25,7 +25,7 @@
       }
 
       :host-context(.focus-outline-visible) #advancedToggle:focus {
-        font-weight: 600;
+        outline: auto 5px -webkit-focus-ring-color;
       }
 
       #osSettingsBanner {