RelNotes/2.2.0.txt: fix minor typos

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
fix typos in old release notes
Fix some misspellings

Signed-off-by: Thomas Ackermann <th.acker@arcor.de>