deskutils/qownnotes: the port had been updated to version 25.6.1

QOwnNotes now expects Botan 3 when built against the system Botan
library due to the end of life of Botan 2, but there is a problem
as Botan 3 requires C++20 which causes issues with Qt 5. To deal
with this discrepancy, provide two flavors: Qt5/QMake-based which
uses bundled Botan 2 amalgamation, and Qt6/CMake-based which uses
Botan library from ports.