Fix integrity check.

jupyterlab/tests/mock_packages/mimeextension/package.json

@@ -3,7 +3,7 @@
   "version": "0.3.0",
   "private": true,
   "dependencies": {
-    "@phosphor/widgets": "^1.5.0"
+    "@phosphor/widgets": "^1.6.0"
   },
   "jupyterlab": {
     "mimeExtension": true