Remove packages that are part of the Spack builds from image

As discussed a while back, it would be a good idea to review and remove from requirements.txt any packages that are part of our EBRAINS Spack builds. This would both reduce the image size and encourage people to use the EBRAINS kernels :)

I just found the table that I'd created a while back for this purpose (generated using this notebook in each kernel) and thought it might help.