Update the ui-components css to reflect the correct dependencies.

packages/ui-components-extension/style/index.css

@@ -3,10 +3,4 @@
 | Distributed under the terms of the Modified BSD License.
 |----------------------------------------------------------------------------*/
 
-/* This file was auto-generated by ensurePackage() in @jupyterlab/buildutils */
-@import url('~@jupyterlab/apputils/style/index.css');
-@import url('~@jupyterlab/rendermime/style/index.css');
-@import url('~@jupyterlab/docregistry/style/index.css');
-@import url('~@jupyterlab/application/style/index.css');
-@import url('~@jupyterlab/notebook/style/index.css');
-@import url('~@jupyterlab/vdom/style/index.css');
+@import url('~@jupyterlab/ui-components/style/index.css');