Fixup extension name typo

I was on autopilot 😆

Author: mfisher87

docker/environment.yml

@@ -11,7 +11,7 @@ dependencies:
   - "jupyter-server-proxy"
   - "jupyterlab-myst"
   - "jupyterlab-geojson"
-  - "jupyterlab_extension_time"
+  - "jupyterlab_execute_time"
   - "nbdime"
 
   # Python mainstays