[css-align-3] Fix the computed value of *-gap

Closes w3c#2294

Author: frivoal

css-align-3/Overview.bs

@@ -1796,7 +1796,7 @@ Row and Column Gutters: the 'row-gap' and 'column-gap' properties</h3>
 	Inherited: no
 	Percentages: refer to corresponding dimension of the content area
 	Media: visual
-	Computed value: as specified, with <<length>>s made absolute, and''row-gap/normal'' computing to zero except on <a>multi-column elements</a>
+	Computed value: as specified, with <<length>>s made absolute
 	Animatable: as length, percentage, or calc
 	</pre>
 
@@ -1830,9 +1830,9 @@ Row and Column Gutters: the 'row-gap' and 'column-gap' properties</h3>
 
 		: <dfn>normal</dfn>
 		:: The ''gap/normal'' represents a UA-dependent length on <a>multi-column elements</a>,
-			and computes to ''0px'' in all other contexts.
+			and a used value of ''0px'' in all other contexts.
 
-			Issue: Should ''gap/normal'' just compute to ''1em'' in multicol?
+			Issue(2145): Should ''gap/normal'' just be ''1em'' in multicol?
 	</dl>
 
 	Gutters effect a minimum spacing between items: