cleanup(): removed unused gfbox style

Author: torkelo

public/sass/_grafana.scss

@@ -54,7 +54,6 @@
 @import "components/gf-form";
 @import "components/sidemenu";
 @import "components/navbar";
-@import "components/gfbox";
 @import "components/timepicker";
 @import "components/filter-controls";
 @import "components/filter-list";