[nautilus] preferences-window: Use correct mnemonic

[Carlos Soriano <csoriano src gnome org>]

commit 9238456bcbfbda9d25cc2f8e55b4fe6e7f14e887
Author: Carlos Soriano <csoriano gnome org>
Date:   Thu Jan 4 18:06:01 2018 +0100

    preferences-window: Use correct mnemonic
    
    An oversight from 611f381d5610

 src/resources/ui/nautilus-preferences-window.ui | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/resources/ui/nautilus-preferences-window.ui b/src/resources/ui/nautilus-preferences-window.ui
index 0b7f53613..0000cc489 100644
--- a/src/resources/ui/nautilus-preferences-window.ui
+++ b/src/resources/ui/nautilus-preferences-window.ui
@@ -929,7 +929,7 @@
                             <property name="can_focus">False</property>
                             <property name="label" translatable="yes">Onl_y for files smaller 
than:</property>
                             <property name="use_underline">True</property>
-                            <property name="mnemonic_widget">preview_image_size_combobox</property>
+                            <property name="mnemonic_widget">preview_image_size_spinbutton</property>
                             <property name="xalign">0</property>
                           </object>
                           <packing>