qt: Use Dialogs foregroundwindow code in confirm
* qt/pinentryconfirm.cpp (PinentryConfirm): Minimize and raise on start. (showEvent): Do not call raiseWindow.
Pinentryconfirm did only partially use the improved foreground window
code from a421ae8c4d2a0ce182e099e634e49ccdad454627.
The raiseWindow in the showEvent was too agressive, which could
result in attaching to a deactivated Window. Which Qt uses
This is not neccessary anymore with the Minimize / Maximize trick.
- GnuPG-Bug-Id: T6135