fix(menu): 🐛 avoid double view button on talk page

In 9969479, we forced the view button to be visible to allow the return action (#845).
There are no good ways to target revision page only so we rely on the diff styles.
However, Extension:DiscussionTools inline the said styles on talk page while talk page also has
a return action registered under the associated page menu. This leaves two button serving the
same function.

skinStyles/mediawiki/mediawiki.diff.styles.less

@@ -64,7 +64,8 @@
 
 // HACK: Restore view button on revision page
 // There are no good way to target revision page
-.action-view #ca-view {
+// The :not selector is needed because Extension:DiscussionTools loads the diff styles inline
+body:not(.ns-talk) .action-view #ca-view {
 	position: relative !important;
 	width: auto;
 	height: auto;