Rename be-x-old language code to be-tarask in languages list (commons-app#5676)

* SettingsFragment: add a method for creating locale

* SettingsFragmentUnitTests: fix failing tests for createLocale

* languages_list: rename be-x-old to be-tarask

Author: rohit9625

app/src/main/res/values/languages_list.xml

@@ -83,7 +83,7 @@
     <item>als</item>
     <item>ig</item>
     <item>su</item>
-    <item>be-x-old</item>
+    <item>be-tarask</item>
     <item>la</item>
     <item>my</item>
     <item>cy</item>