vim: don't use deprecated vam attribute

[getchoo]

As of https://github.com/NixOS/nixpkgs/pull/179039 (~22.11), the vam attribute of vimrcConfig has been deprecated. This moves the module to the recommend packages attribute, removing the trace most systems will come across currently and making adding plugins a little bit easier. The default "sensible" plugins have also been replaced with the less opinionated vim-sensible - similar to home-manager.

This is a breaking change