Qt: Use SEX_xxx macros for selected_sex variable in dialogs.cpp
#42937 introduces SEX_UNKNOWN, SEX_MALE, and SEX_FEMALE macros. Use them instead of magic values in Qt-clients leader selection ('selected_sex' variable in dialogs.cpp)
Patch rewritten on top of #42964
#42937 introduces SEX_UNKNOWN, SEX_MALE, and SEX_FEMALE macros. Use them instead of magic values in Qt-clients leader selection ('selected_sex' variable in dialogs.cpp)