change class name for BG overlib see @ https://github.com/librenms/librenms/pull/10300

html/css/custom/styles.css

@@ -649,7 +649,7 @@ legend {
 }
 
 /* OVERLIB BG*/
-.lib_overlib {
+.overlib-contents {
     background: inherit;
     background-color: #333;
     color:cyan;