Optional run-dependency fpc-gtk2 (russian/emkatic)

[Andrey Fesenko]

Hello,

After https://reviews.freebsd.org/rP376735 port russian/emkatic began
to require fpc-gtk2 as RUN_DEPENDS. Although it is actually it is for
his work is not needed, and needed only BUILD_DEPENDS.

I understand this is a consequence USE_FPC+= gtk2 USE_GNOME= gtk20

It is strictly necessary behavior or accident? since it leads to the
setting in general is not required packages for users who do not BUILD
this port.