Bug 1600804 - add permissive fuzzy-if annotation to checkbox-clamp-02.html r=jmaher

Changes:

Insert permissive `fuzzy-if` annotation to the test to accommodate ubuntu1804 where the test fails due to large pixel difference.

Once the migration completes the pixel difference value will be tightened.

Differential Revision: https://phabricator.services.mozilla.com/D57229

--HG--
extra : moz-landing-system : lando

layout/reftests/forms/input/checkbox/reftest.list

@@ -15,5 +15,5 @@ skip-if(!gtkWidget) == gtk-theme-width-height.html gtk-theme-width-height-ref.ht
 == checkbox-baseline.html checkbox-baseline-ref.html
 == checkbox-radio-color.html checkbox-radio-color-ref.html
 skip-if(gtkWidget) fails-if(geckoview&&webrender) == checkbox-clamp-01.html checkbox-clamp-01-ref.html
-skip-if(OSX||winWidget) fails-if(geckoview&&webrender) == checkbox-clamp-02.html checkbox-clamp-02-ref.html
+skip-if(OSX||winWidget) fails-if(geckoview&&webrender) fuzzy-if(gtkWidget,0-25,0-32) == checkbox-clamp-02.html checkbox-clamp-02-ref.html
 fails-if(OSX) == checkbox-minimum-size.html checkbox-minimum-size-ref.html