Integrity updates to fix an error from removing vega4

dev_mode/imports.css

@@ -35,5 +35,4 @@
 @import url('~@jupyterlab/tooltip-extension/style/index.css');
 @import url('~@jupyterlab/ui-components-extension/style/index.css');
 @import url('~@jupyterlab/vdom-extension/style/index.css');
-@import url('~@jupyterlab/vega4-extension/style/index.css');
 @import url('~@jupyterlab/vega5-extension/style/index.css');