Typos in grid.md

Created by: Rychu-Pawel

Fixed typos in offsetting section of grid.md

docs/4.0/layout/grid.md

@@ -590,7 +590,7 @@ In addition to column clearing at responsive breakpoints, you may need to reset
 </div>
 
 <div class="row">
-  <div class="col-sm-6 col-md-5 col-lg-6">.col.col-sm-6.col-md-5.col-lg-6</div>
+  <div class="col-sm-6 col-md-5 col-lg-6">.col-sm-6 .col-md-5 .col-lg-6</div>
   <div class="col-sm-6 col-md-5 offset-md-2 col-lg-6 offset-lg-0">.col-sm-6 .col-md-5 .offset-md-2 .col-lg-6 .offset-lg-0</div>
 </div>
 {% endexample %}