Fix sorting behavior layout independent

The respective css styling is moved out of the case distinction between
grid and flexbox layout to be indpendent of the layout choice.

src/sass/components/_content.scss

@@ -28,6 +28,7 @@
 
 #content {
   padding: $padding-side;
+  overflow-x: auto; // needed for drag & drop of enumerations
 
   @if $css-grid-layout {
     grid-area: content;
@@ -35,7 +36,6 @@
     $side-space: $sidebar-width + $padding-side * 2;
     flex: 1 1 auto;
     width: calc(100% - #{$side-space});
-    overflow-x: auto; // needed for drag & drop of enumerations
   } @else {
     overflow: hidden;
   }