Bug 1599697 - Re-add 'font: inherit' to .tree-input. r=dao

Differential Revision: https://phabricator.services.mozilla.com/D54918

--HG--
extra : moz-landing-system : lando

toolkit/themes/shared/tree.inc.css

@@ -200,6 +200,7 @@ html|input.tree-input {
   margin: 0;
   margin-inline-start: -4px;
   padding: 1px;
+  font: inherit;
 }
 
 .scrollbar-topmost {