Keep middle click paste enabled for now

We're not really ready for this change, and we haven't
messaged it properly. After discussion with Allan Day and
Jakup Steiner, we'll defer this change until the next cycle.

plugins/xsettings/gsd-xsettings-manager.c

@@ -348,7 +348,7 @@ static FixedEntry fixed_entries [] = {
         { "Gtk/ShowInputMethodMenu", fixed_false_int },
         { "Gtk/ShowUnicodeMenu",     fixed_false_int },
         { "Gtk/AutoMnemonics",       fixed_true_int },
-        { "Gtk/EnablePrimaryPaste",  fixed_false_int },
+        { "Gtk/EnablePrimaryPaste",  fixed_true_int },
 };
 
 static TranslationEntry translations [] = {