update the gallery link in FAQ (#5670)

src/olympia/pages/templates/pages/faq.html

@@ -243,7 +243,7 @@
 
     <dt>{{ _('What are mobile add-ons?') }}</dt>
     <dd>{% trans mobile_url="https://www.mozilla.org/firefox/android/",
-           gallery_url=locale_url('mobile') %}
+           gallery_url=locale_url('android') %}
         Mobile add-ons work with <a href="{{ mobile_url }}">Firefox for
         Android</a> and add or modify functionality just like desktop add-ons.
         You can find add-ons that work with Firefox for Android in our