help still refer to ipython kernel install

[Carreau]

And ipython-kernel-install does not point to python -m ipykernel install, though the docs ask to use it.

Having consistent information would be helpful.

[minrk]

ipython kernel install works and continues to be correct. ipython kernel and python -m ipykernel are equivalent, including subcommands passed to them. It's analogous to when one would use pip vs python -m pip.

I agree that we should be more careful and consistent.