amd64, i386: remove profile directive from NOTES

Support for this directive has been removed in config(8) on main,
which leaves us unable to build LINT with newer config(8). It's
believed that mcount-based profiling didn't really work on modern
systems anyways, so the value of testing this is low.

We avoid providing limited backwards compatibility here to continue and
warn folks that may somehow be deploying real-world configs with profile
specified.

This is a direct commit to stable/12, but a partial MFC of aa3ea612be36.