Based on UI designer folks requirement, change the default font size in ChromeOS from 12px to 13px.

BUG=449675
TEST=zha@, sgabriel@ manually checked on devices (1x, 2x)

Review URL: https://codereview.chromium.org/887153002

Cr-Commit-Position: refs/heads/master@{#314363}

ui/strings/app_locale_settings.grd

@@ -256,7 +256,7 @@
       <if expr="chromeos">
         <!-- The font name like: 'Font Name, 10' -->
         <message name="IDS_UI_FONT_FAMILY_CROS" use_name_for_id="true">
-          Noto Sans UI, 12px
+          Noto Sans UI, 13px
         </message>
 
         <!-- The font used in Web UI (e.g. History). -->