[css-contain-1] Fix typo in changelog

Author: frivoal

css-contain-1/Overview.bs

@@ -1171,7 +1171,7 @@ This appendix is <em>informative</em>.
 <a href="https://www.w3.org/TR/2019/CR-css-contain-1-20190430/">Candidate Recommendation of 30 April 2019</a></h3>
 
 	Full Dispositions of Comments <a href="https://drafts.csswg.org/css-contain-1/issues-2019-cr">since CR</a>
-	and <a href="https://drafts.csswg.org/css-contain-1/issues-2019-10-pr">since PR</a> PR is available.
+	and <a href="https://drafts.csswg.org/css-contain-1/issues-2019-10-pr">since PR</a> is available.
 
 	<ul>
 		<li>