Trac #31372: pari_jupyter is not compatible with python 3.9, breaks docker build on gitlab

(from https://groups.google.com/g/sage-release/c/hVIsURxpdhc/m/0h-
_jT6mCQAJ)

reported upstream at sagemath/pari-jupyter#9

As a fix, we remove the step that tries to install 3 optional packages
that the `Dockerfile` installs in addition to standard packages.

URL: https://trac.sagemath.org/31372
Reported by: mkoeppe
Ticket author(s): Matthias Koeppe
Reviewer(s): Frédéric Chapoton

Author: Release Manager

docker/Dockerfile

@@ -186,12 +186,9 @@ ENV SAGE_NUM_THREADS $SAGE_NUM_THREADS_DOCBUILD
 RUN make
 
 ################################################################################
-# Image with a full build of sage, ready to release, i.e., with stripped       #
-# binaries and some extras to run the jupyter notebook.                        #
+# Image with a full build of sage, ready to release.                           #
 ################################################################################
 FROM make-all as make-release
-RUN sage -pip install terminado "notebook>=5" "ipykernel>=4.6"
-RUN sage -i gap_jupyter singular_jupyter pari_jupyter
 RUN make micro_release
 
 ################################################################################