Simplify padding definition and center text (ankitects#2308)

Author: kleinerpirat

qt/aqt/data/web/css/toolbar.scss

@@ -72,7 +72,7 @@ body {
 
 .hitem {
     font-weight: bold;
-    padding: 6px 12px 8px;
+    padding: 5px 12px;
     text-decoration: none;
     color: color(fg);
     display: inline-block;