sourceview: Remove mysteriously-activated GtkSourceView bindings

These bindings are explicitly for Alt+Shift+KP_Down/Up, and yet they're
being activated by just Alt+KP_Down/Up.

See GNOME/gtk#140

Author: kaiw

meld/sourceview.py

@@ -132,8 +132,10 @@ def set_show_line_numbers(self, show):
         # We replace the default line movement behaviour of Alt+Up/Down
         (Gdk.KEY_Up, Gdk.ModifierType.MOD1_MASK),
         (Gdk.KEY_KP_Up, Gdk.ModifierType.MOD1_MASK),
+        (Gdk.KEY_KP_Up, Gdk.ModifierType.MOD1_MASK | Gdk.ModifierType.SHIFT_MASK),
         (Gdk.KEY_Down, Gdk.ModifierType.MOD1_MASK),
         (Gdk.KEY_KP_Down, Gdk.ModifierType.MOD1_MASK),
+        (Gdk.KEY_KP_Down, Gdk.ModifierType.MOD1_MASK | Gdk.ModifierType.SHIFT_MASK),
         # ...and Alt+Left/Right
         (Gdk.KEY_Left, Gdk.ModifierType.MOD1_MASK),
         (Gdk.KEY_KP_Left, Gdk.ModifierType.MOD1_MASK),