Adjust header bar shadow in dark.css theme

install/deb/themes/dark.css

@@ -784,7 +784,7 @@ a {
   z-index: 900;
   height: 38px;
   text-shadow: 1px 1px rgba(0,0,0,0.5);
-  box-shadow: 0px 8px 20px rgba(0,0,0,0.35);
+  box-shadow: 0px 8px 15px rgba(0,0,0,0.25);
 }
 
 .l-header a {