FIX: -c plolty not giving a recent enough version of plotly

Author: mmcky

lectures/back_prop.md

@@ -21,8 +21,8 @@ In addition to what's included in base Anaconda, we need to install the followin
 ```{code-cell} ipython3
 :tags: [hide-output]
 
-!pip install -U kaleido
-!conda install -y -c plotly plotly plotly-orca retrying
+!pip install -U kaleido plotly
+!conda install -y -c plotly plotly-orca
 ```
 
 We also need to install JAX to run this lecture