Remove filter names stored in libkleopatrarc

The filter names should never have been written to libkleopatrarc, but
previously translated filter names were written to libkleopatrarc when
the appearence filters were configured. This migration cleans this up.

(cherry picked from commit f2afdc44ad2824e48e5f085963b5636d326b2c48)

• GnuPG-bug-id: T7612