qt: Report better error if decryption failed because of bad passphrase
* lang/qt/src/qgpgmedecryptverifyjob.cpp (patch_decryption_result): New. (decrypt_verify): Call patch_decryption_result.
Replace the generic "decryption failed" error with the more specific
"bad passphrase" error if the audit log indicates that a wrong symmetric
password caused the decryption to fail.
- GnuPG-bug-id: T5939