[css-grid] Fix markup

Author: fantasai

css-grid/Overview.bs

@@ -2880,7 +2880,7 @@ Gutters: the 'column-gap', 'row-gap', and 'grid-gap' properties</h3>
 
 	On <a>grid containers</a>, a value of <dfn for="row-gap,column-gap" dfn-type=value>normal</dfn> computes to zero.
 
-	Issue: Should we have grid-specific properties for this (e.g. 'grid-row-gap')
+	Issue: Should we have grid-specific properties for this (e.g. <css>grid-row-gap</css>)
 	instead of sharing with multicol ('row-gap')?
 	Sharing with multi-col could be problematic if we re-use the 'grid-template'
 	properties to set up <a href="http://www.w3.org/TR/css-line-grid-1/">grid-snapping</a>.