Uninstall nbclassic on Binder so Notebook v7 can load (#6505)

* Try force reinstalling on Binder

* uninstall nbclassic

* Update postBuild

* Add comment about uninstall nbclassic

Author: jtpio

binder/postBuild

@@ -1,6 +1,11 @@
 #!/bin/bash
 set -euo pipefail
 
-python -m pip install -e .
+python -m pip install -e . --force-reinstall
+
+# TODO: remove when it's possible to install nbclassic next to Notebook v7
+# without nbclassic shadowing the v7 endpoints
+python -m pip uninstall nbclassic -y
+
 jlpm && jlpm run build
 jlpm run develop