Qt: Disable automatic wrap for desc and errors

* qt/pinentrydialog.cpp (PinEntryDialog): Disable WordWrap.

The agent already sends line breaks which should be respected.
This fixes the problem that pinentry-qt would break ssh fingerprints
because it treated the colon as a breakable character.

GnuPG's translators and GnuPG itself should take care how descriptions
and errors should be formatted.