[css-align] Clarify previous commit - left/right are allowed in justify-items as well.

Author: tabatkins

css-align-3/Overview.bs

@@ -362,9 +362,9 @@ Positional Alignment: the ''center'', ''start'', ''end'', ''self-start'', ''self
 	</dl>
 
 	Note: ''left'' and ''right'' are excluded from <<self-position>>,
-	despite being valid [=positional alignment=] values for 'justify-self',
+	despite being valid [=positional alignment=] values for 'justify-self'/'justify-items',
 	because they are not allowed in 'align-self'.
-	They are instead explicitly included in the 'justify-self' grammar.
+	They are instead explicitly included in the 'justify-self' and 'justify-items' grammars.
 
 	<aside class=example>
 		The ''<self-position>/start'' and ''<self-position>/end'' keywords