Bug 1240894 - Make new tab button always visible regardless of position of close tab button r=Ratty

suite/mailnews/messenger.css

@@ -192,11 +192,6 @@ dummy.usesMailWidgets {
 
 .tabs-newbutton {
   -moz-binding: url("chrome://messenger/content/tabmail.xml#tabmail-new-tab-button");
-  display: none;
-}
-
-.tabmail-tabs[closebuttons="closeatend"] .tabs-newbutton {
-  display: -moz-box;
 }
 
 .tab-close-button,