Use separate class for tippy targets (#20742)

Previous solution that re-purposed the 'hide' class by making it
`!important` had various unintended side-effects where jQuery .show() was
not able to outweight it. Use a separate class to prevent these
interactions.

web_src/less/_base.less

@@ -1315,7 +1315,7 @@ footer {
 }
 
 .hide {
-  display: none !important;
+  display: none;
 
   &.show-outdated {
     display: none !important;