Fix sr locale being selected over sr-Latn (#13693)

* Fix sr locale being selected over sr-Latn

* Update tests

config/application.rb

@@ -55,8 +55,8 @@ module Mastodon
       :el,
       :en,
       :eo,
-      :'es-AR',
       :es,
+      :'es-AR',
       :et,
       :eu,
       :fa,
@@ -97,8 +97,8 @@ module Mastodon
       :sk,
       :sl,
       :sq,
-      :'sr-Latn',
       :sr,
+      :'sr-Latn',
       :sv,
       :ta,
       :te,