[css-align] Remove stray '3' character.

Author: dbaron

css-align/Overview.bs

@@ -1322,7 +1322,7 @@ Self-Alignment Shorthand: the 'place-self' property</h3>
 	Inherited: no
 	Percentages: n/a
 	Media: visual
-	Computed value: see individual properties3
+	Computed value: see individual properties
 	Animatable: no
 	</pre>