revert ipywidgets version pinning which didn't work

(see jupyter/try-jupyter#54 (comment))

requirements.txt

@@ -16,8 +16,4 @@ jupyterlab-language-pack-zh-CN
 jupyterlab-night
 
 # Python: ipywidget library for Jupyter notebooks (optional)
-# !temporary pinning in relation to https://github.com/jupyter/try-jupyter/issues/54#issuecomment-2363763889
-ipywidgets<8.1.3
-jupyterlab_widgets==3.0.12
-# Python: interative Matplotlib library for Jupyter notebooks (optional)
-ipympl>=0.8.2
+ipywidgets>=8.1.3,<9