gui: pin GdkPixbuf 2.0 to remove PyGI warning

Author: vassilit

gui/shredder/__init__.py

@@ -3,6 +3,7 @@
 import gi
 
 gi.require_version('Gtk', '3.0')
+gi.require_version('GdkPixbuf', '2.0')
 gi.require_version('Rsvg', '2.0')
 gi.require_version('PangoCairo', '1.0')
 gi.require_version('GtkSource', '4')
@@ -21,10 +22,8 @@
 
 def run_gui():
     """Fully take over and run the gui code."""
-    # Stdlib:
     import sys
 
-    # Internal:
     from shredder.cmdline import parse_arguments
     from shredder.logger import create_logger