docs: fix table custom filter docs (#8078)

Author: angelod1as

components/doc/datatable/filter/customdoc.js

@@ -644,6 +644,7 @@ export default function CustomFilterDemo() {
                 <Column header="Country" filterField="country.name" style={{ minWidth: '12rem' }} body={countryBodyTemplate} filter filterPlaceholder="Search by country" />
                 <Column header="Agent" filterField="representative" showFilterMenu={false} filterMenuStyle={{ width: '14rem' }} style={{ minWidth: '14rem' }}
                     body={representativeBodyTemplate} filter filterElement={representativeRowFilterTemplate} />
+                <Column header="Activity(Custom Filter)" field="activity" showFilterMenu={false} showClearButton={false} style={{ minWidth: "14rem" }} filter filterElement={activityRowFilterTemplate} />
                 <Column field="status" header="Status" showFilterMenu={false} filterMenuStyle={{ width: '14rem' }} style={{ minWidth: '12rem' }} body={statusBodyTemplate} filter filterElement={statusRowFilterTemplate} />
                 <Column field="verified" header="Verified" dataType="boolean" style={{ minWidth: '6rem' }} body={verifiedBodyTemplate} filter filterElement={verifiedRowFilterTemplate} />
             </DataTable>