gitignore: drop duplicate entry for git-sh-i18n

This was accidentally added by e00cf070a4 (git-sh-i18n.sh: add no-op
gettext() and eval_gettext() wrappers, 2011-05-14), even though an
earlier commit in the same series had already done so.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

.gitignore

@@ -151,7 +151,6 @@
 /git-sh-i18n
 /git-sh-i18n--envsubst
 /git-sh-setup
-/git-sh-i18n
 /git-shell
 /git-shortlog
 /git-show