[css-overflow-3] fix link to commit history (#11965)

Author: myakura

css-overflow-3/Overview.bs

@@ -1350,7 +1350,7 @@ Changes Prior to the <a href="https://www.w3.org/TR/2018/WD-css-overflow-3-20180
 	Changes predating the publication of the <a href="https://www.w3.org/TR/2018/WD-css-overflow-3-20180731/">2018-07-31 Working Draft</a>
 	can be found in the following change logs:
 
-	* <a href="https://github.com/w3c/csswg-drafts/commits/master?path=css-overflow-3&until=2018-07-31">from 2017-08-02 to 2018-07-31</a>
+	* <a href="https://github.com/w3c/csswg-drafts/commits/main?path=css-overflow-3&until=2018-07-31">from 2017-08-02 to 2018-07-31</a>
 	* <a href="https://hg.csswg.org/drafts/log/tip/css-overflow/Overview.bs">from 2015-01-27 to 2017-08-01</a>
 	* <a href="https://hg.csswg.org/drafts/log/tip/css-overflow/Overview.src.html">from 2013-03-28 to 2015-01-27</a>
 	* <a href="https://hg.csswg.org/drafts/log/tip/css3-overflow/Overview.src.html">from 2012-07-31 to 2013-03-27</a>