Explaining BSD: add a full stop

Comparing BSD and Linux – How is BSD developed and updated?

https://docs.freebsd.org/en/articles/explaining-bsd/#_how_is_bsd_developed_and_updated

'On the other hand, developers making far-reaching or complicated
changes are expected to submit their changes for review before
committing them In extreme cases, a core team member with a function
such as Principal Architect may order that changes be removed from the
tree, a process known as backing out.'

– is missing a period after 'before committing them'.

Reported-by: soobinrho (GitHub)
Signed-off-by: Soobin Rho <soobinrho@gmail.com>
Approved-by: grahamperrin
Fixes: e16d21085b Fix typos, style and images paths
Pull-request: https://github.com/freebsd/freebsd-doc/pull/201