website: fix MFC glossary links

MFC links are incorrectly redirected to the main handbook, not the
glossary subdirectory. Mechanically rewrite to redirect to the right
place. Change all the redirections from
https://docs.freebsd.org/en/books/handbook/#mfc-glossary
to
https://docs.freebsd.org/en/books/handbook/glossary/#mfc-glossary

PR: 276851
Reviewed by: imp