Fix ash_shell_with_content fingerprint dependency

Ash has a transitive dependency on the device fingerprint service, so
the test-only ash_shell_with_content won't start up without
declaring that requirement.

Bug: none
Test: run ash_shell_with_content, it starts
Change-Id: Id8acd41c154738a9470b8b19f63da93fede1740f
Reviewed-on: https://chromium-review.googlesource.com/c/1329623Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606910}

ash/shell/ash_content_browser_manifest_overlay.json

@@ -4,7 +4,8 @@
   "interface_provider_specs": {
     "service_manager:connector": {
       "requires": {
-        "shortcut_viewer_app": [ "shortcut_viewer" ]
+        "shortcut_viewer_app": [ "shortcut_viewer" ],
+        "device": [ "device:fingerprint" ]
       }
     }
   }