Remove useless import

Author: louismaximepiton

scss/bootstrap-grid.scss

@@ -8,7 +8,6 @@ $include-column-box-sizing: true !default;
 @import "variables-dark";
 @import "maps";
 
-@import "mixins/lists";
 @import "mixins/breakpoints";
 @import "mixins/container";
 @import "mixins/grid";