cfg/gtk.cfg: Remove incorrect GIOChannel destructors

`shutdown` and `close` methods do not actually unref the channel:

    The channel will not be freed until the last reference is dropped using g_io_channel_unref().

https://docs.gtk.org/glib/method.IOChannel.close.html
https://docs.gtk.org/glib/method.IOChannel.shutdown.html

Author: jtojnar

cfg/gtk.cfg

@@ -631,8 +631,6 @@
     <alloc init="true" no-fail="true">g_io_channel_win32_new_messages</alloc>
     <alloc init="true" no-fail="true">g_io_channel_new_file</alloc>
     <use>g_io_channel_ref</use>
-    <dealloc>g_io_channel_close</dealloc>
-    <dealloc>g_io_channel_shutdown</dealloc>
     <dealloc>g_io_channel_unref</dealloc>
   </memory>
   <memory>