feat(style): organize and cleanup

Author: GeopJr

data/gtk/dropdown/expiration_title.ui

@@ -8,7 +8,7 @@
           </lookup>
         </binding>
         <style>
-          <class name="locale-dropdown-upcase"/>
+          <class name="uppercase"/>
         </style>
       </object>
     </property>

data/gtk/dropdown/language_title.ui

@@ -17,7 +17,7 @@
               </lookup>
             </binding>
             <style>
-              <class name="locale-dropdown-upcase"/>
+              <class name="uppercase"/>
             </style>
           </object>
         <!-- </child>