bump soversion ahead of release alongside 6th megarelease
KDiagram needs a Qt6 based release ahead of KDE's 6th Megarelease so distros can ship KDE PIM (which uses kgantt) and keep the Qt 5 version (KChart is used by massif-visulaiser, calligra, kmymoney and heaptrack)
Bump soversion and release would be acceptable I think.