gpg: Fixed i18n markup of some strings.

* g10/tofu.c: Removed some translation markups which either make no
sense or are not possble.

Error message which are not helpful for the user but indicate a
problem of the installation or the code do not need a translation.
The translator may not understand them correctly and the use support
can't immediately locate the problem because it needs to be reverse
translated.

There is also one case where certain grammar constructs are
assumed (concatenating parts of a sentence at runtime). Better do not
translate that than getting weird sentences.