chore(*): Enable back grid cell tests.

Author: MKirova

projects/igniteui-angular/src/lib/grids/grid/cell.spec.ts

@@ -151,7 +151,7 @@ describe('IgxGrid - Cell component #grid', () => {
         });
     });
 
-    xdescribe('Cells in virtualized grid ', () => {
+    describe('Cells in virtualized grid ', () => {
         let fix;
         let grid: IgxGridComponent;