passworddialog.cpp: include QIcon explicitely
passworddialog.cpp: include QIcon explicitely

5.11 Qt headers do not indirectly include QIcon resulting in compile
time errors like:
| passworddialog.cpp:44:33: error: incomplete type 'QIcon' used in nested name specifier

Signed-off-by: Max Krummenacher <2adf29ceaf73d2cea8fff1ff57e7b25e74cc8f1f@toradex.com>

lxde/lxqt-sudo