[web-animations-1] Update a few links to point to main branch instead of master

Author: birtles

web-animations-1/Overview.bs

@@ -85,11 +85,11 @@ Previous version: https://www.w3.org/TR/2016/WD-web-animations-1-20160913/
 Previous version: https://www.w3.org/TR/2015/WD-web-animations-1-20150707/
 Previous version: https://www.w3.org/TR/2014/WD-web-animations-20140605/
 Previous version: https://www.w3.org/TR/2013/WD-web-animations-20130625/
-Version history: https://github.com/w3c/csswg-drafts/commits/master/web-animations-1
+Version history: https://github.com/w3c/csswg-drafts/commits/main/web-animations-1
 Level: 1
 
 Group: csswg
-!Participate: <a href="https://github.com/w3c/csswg-drafts/tree/master/web-animations-1">Fix the text through GitHub</a>
+!Participate: <a href="https://github.com/w3c/csswg-drafts/tree/main/web-animations-1">Fix the text through GitHub</a>
 !Participate: Join the &lsquo;waapi&rsquo; channel on the <a href="https://damp-lake-50659.herokuapp.com/">Animation at Work</a> slack
 !Participate: IRC: <a href="ircs://irc.w3.org:6667/webanimations">#webanimations</a> on W3C's IRC
 Repository: w3c/csswg-drafts
@@ -6387,7 +6387,7 @@ The following changes have been made since the <a
     so that it can be used with {{ShadowRoot}}s as well.
 
 The <a
-  href="https://github.com/w3c/csswg-drafts/commits/master/web-animations-1">changelog</a>
+  href="https://github.com/w3c/csswg-drafts/commits/main/web-animations-1">changelog</a>
 provides a more detailed history.