i18n: fix typos found during l10n for git 2.34.0

i18n: fix typos found during l10n for git 2.34.0

Emir and Jean-Noël reported typos in some i18n messages when preparing
l10n for git 2.34.0.

* Fix unstable spelling of config variable "gpg.ssh.defaultKeyCommand"
  which was introduced in commit fd9e226776 (ssh signing: retrieve a
  default key from ssh-agent, 2021-09-10).

* Add missing space between "with" and "--python" which was introduced
  in commit bd0708c7eb (ref-filter: add %(raw) atom, 2021-07-26).

* Fix unmatched single quote in 'builtin/index-pack.c' which was
  introduced in commit 8737dab346 (index-pack: refactor renaming in
  final(), 2021-09-09)

[1] https://github.com/git-l10n/git-po/pull/567

Reported-by: Emir Sarı <bitigchi@me.com>
Reported-by: Jean-Noël Avila <jn.avila@free.fr>
Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>