Fix an issue with the default-data-table-content-body component

It seems we accidentally prefixed a block variable with `this` when resolving some deprecation warnings.

Author: Windvis

addon/components/au-data-table/default-data-table-content-body.hbs

@@ -13,7 +13,7 @@
 {{#each this.otherColumns as |field|}}
   <td>
     {{! This should be based on the type of the field }}
-    {{get this.item this.field}}
+    {{get this.item field}}
   </td>
 {{/each}}
 {{yield}}