Deprecate Tcl/Tk 8.5 and dependent ports

Tcl/Tk 8.5 is approaching EOL. It might or might get another patch release with
8.7 is released, but people should have started migrating to 8.6 long ago. See
also the second paragraph in the last 8.5 release announcement from three years
ago here: https://code.activestate.com/lists/tcl-core/15413/

For now, I don't have an EXPIRATION_DATE.