Revert "g10: Fix singular term."

This reverts commit b0d2526bc4e5c663eeffe04500420c70cee98712.

The number of format elements may not change in ngettext. The entire
construct is anyway wrong because ngettext is passed a different value
than what is used in the printf.

We need to rework the use of most strings in tofu.c.

• Signed-off-by: Werner Koch <wk@gnupg.org>