Deprecate %params line magic

I had completely forgotten param provided the `%params` line magic for IPython.


`%params` is not documented on the website. I'm in favor of deprecating it, although there's a catch. While I think the HTML repr is a better alternative in a notebook, there would no longer be an easy way to display the custom IPython repr in an IPython console (`print(param.parameterized.param_pager())`); `?` displays the *class* docstring and not the current values of the instance.

From a [quick search](https://ipython.readthedocs.io/en/8.26.0/config/integrating.html#custom-methods), implementing `_repr_pretty_` seems to be the way for an object to have both a fancier IPython repr and an HTML repr (already implemented with `_repr_html_`). I think that would mean that the implementation wouldn't be as a pager (https://ipython.readthedocs.io/en/8.26.0/api/generated/IPython.lib.pretty.html) but I'm not sure to which extent the pager is useful, is the repr long enough to justify it?