CSS: Update @font-family-fixed

Author: flourish86

public/css/icinga/base.less

@@ -94,7 +94,7 @@
 
 // Font families
 @font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
-@font-family-fixed: "Liberation Mono", "Lucida Console", Courier, monospace;
+@font-family-fixed: ui-monospace, SFMono-Regular, SF Mono, Menlo, Consolas, Liberation Mono, monospace;
 @font-family-wide: Tahoma, Verdana, sans-serif;
 
 // Font sizes