fixed doubled offcanvas menu in boxed layout

build/scss/_control-sidebar.scss

@@ -70,8 +70,7 @@
   }
 
   //  Background
-  &,
-  &::before {
+  & {
     background: $sidebar-dark-bg;
   }
 
@@ -140,8 +139,7 @@
   color: lighten($sidebar-light-color, 10%);
 
   //  Background
-  &,
-  &::before {
+  & {
     background: $sidebar-light-bg;
     border-left: 1px solid $gray-500;
   }

dist/css/adminlte.css

@@ -11701,7 +11701,7 @@ body,
   color: #C2C7D0;
 }
 
-.control-sidebar-dark, .control-sidebar-dark::before {
+.control-sidebar-dark {
   background: #343a40;
 }
 
@@ -11759,7 +11759,7 @@ body,
   color: #4b545c;
 }
 
-.control-sidebar-light, .control-sidebar-light::before {
+.control-sidebar-light {
   background: #ffffff;
   border-left: 1px solid #adb5bd;
 }