[css-ruby-1] typo

Author: fantasai

css-ruby-1/Overview.bs

@@ -482,7 +482,7 @@ Annotation Pairing</h3>
 	(A [=ruby annotation=] that [=spans=] multiple bases is called
 	a <dfn>spanning annotation</dfn>.)
 
-	A [=ruby base=] is can be associated with
+	A [=ruby base=] can be associated with
 	only one [=ruby annotation=] per [=annotation level=].
 	However, if there are multiple [=annotation levels=],
 	it can be associated with multiple [=ruby annotations=].