graphics/darktable40 removal

From: Jonathan Chen <jonc_at_chen.org.nz>
Date: Fri, 23 Sep 2022 05:12:32 UTC
Hi,

graphics/darktable40 was removed with commit db691c4, but 
graphics/Makefile still has a reference to it:

5:09pm# grep darktable /usr/ports/graphics/Makefile
     SUBDIR += darktable
     SUBDIR += darktable40

Any committer present to just-fix-it?

Cheers.
--
Jonathan Chen <jonc@chen.org.nz>