Rack assignment is optional for devices

netbox/templates/dcim/device_import.html

@@ -73,7 +73,7 @@
 				</tr>
 				<tr>
 					<td>Rack</td>
-					<td>Rack name</td>
+					<td>Rack name (optional)</td>
 					<td>R101</td>
 				</tr>
 				<tr>