bumping jupyterlab version to the latest stable version

The previous jupyterlab version was quite old and lacked several features. I've done a test run with the latest stable version and didn't experience any issues. The jupyter-server requirement also doesn't really seem to be necessary, as jupyterlab will automatically install the corresponding jupyter-server version

requirements.txt

@@ -1,4 +1,3 @@
-jupyterlab==3.6.1
-jupyter-server==2.3.0
+jupyterlab==4.2.5
 tornado==6.2
 ipywidgets