Revert changes to Copy text popups, to let them more consistently copy

Author: Numynum

TalentTreeViewer/TalentViewerUIMixin.lua

@@ -757,7 +757,7 @@ do
             end
             dialog.editBox:SetScript("OnEscapePressed", HidePopup);
             dialog.editBox:SetScript("OnEnterPressed", HidePopup);
-            dialog.editBox:SetScript("OnKeyDown", function(_, key)
+            dialog.editBox:SetScript("OnKeyUp", function(_, key)
                 if IsControlKeyDown() and key == "C" then
                     HidePopup();
                 end