Qt: Don't declare showErrorDialog anymore
Qt: Don't declare showErrorDialog anymore

* cpp/qt/src/job.h: Remove showErrorDialog.

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If additional error handling is neccessary emitting
signals to a gui application would be better API for qgpgme.

gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme