sys/sys/param.h: 'main' instead of 'Master'?

[Ed Maste]

On Fri, 16 Apr 2021 at 16:22, Warner Losh <imp at bsdimp.com> wrote:
>
> > > As well as "Origin".
> >
> > (Single) Source of Truth, maybe?
>
> s/Master, p/P/ also makes sense.

IMO instead of lightly rewording the existing comment we could just
remove it, it doesn't really add any clarity.

Instead we ought to add an introductory sentence or two to the block
comment above, explaining what __FreeBSD_version actually is.