Bug 1599622 - add permissive annotation for gtkWidget to radio-clamp-02.html test for ubuntu1804 r=jmaher

Changes:

Annotate the reftest failure on ubuntu1804 with a permissive `fuzzy-if` annotation designed to work with both ubuntu1604 and ubuntu1804.

Once the switchover to ubuntu1804 takes place, tighten the pixel range such that future failures can be caught.

Differential Revision: https://phabricator.services.mozilla.com/D55030

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

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

@@ -6,5 +6,5 @@
 != checked-native-notref.html about:blank
 skip-if(!gtkWidget) == gtk-theme-width-height.html gtk-theme-width-height-ref.html
 skip-if(gtkWidget) fails-if(geckoview&&webrender) == radio-clamp-01.html radio-clamp-01-ref.html
-skip-if(OSX||winWidget) == radio-clamp-02.html radio-clamp-02-ref.html
+skip-if(OSX||winWidget) fuzzy-if(gtkWidget,0-24,0-16) == radio-clamp-02.html radio-clamp-02-ref.html # bug 1599622 for gtkWidget
 fails-if(OSX) == radio-minimum-size.html radio-minimum-size-ref.html