This static function has no callers, nor has it had any since its
introduction in ba67aaf2d05d (git-sh-i18n--envsubst: our own envsubst(1)
for eval_gettext(), 2011-05-14). Remove it.
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>