Remove one GDK_question. Trivial one-line fix

widget/src/gtk/nsGtkEventHandler.cpp

@@ -209,7 +209,6 @@ struct nsKeyConverter nsKeycodes[] = {
   // Some shifted keys, see bug 15463.
   // These should be subject to different keyboard mappings;
   // how do we do that in gtk?
-  { NS_VK_SLASH,      GDK_question },
   { NS_VK_SEMICOLON, GDK_colon },
   { NS_VK_BACK_QUOTE, GDK_asciitilde },
   { NS_VK_COMMA, GDK_less },