Fixed error in documentation in mixins.less

less/mixins.less

@@ -618,7 +618,7 @@
   }
 }
 
-// Generate the large column offsets
+// Generate the medium column offsets
 .make-md-column-offset(@columns) {
   @media (min-width: @screen-md-min) {
     margin-left: percentage((@columns / @grid-columns));