Fix fetch of graphics/gmic-qt distfile "gmic_stdlib.h"

gmic has had a versioned "stdlib" data file since 2018, as
described in https://github.com/dtschump/gmic/issues/61 ,
but the port always referred to an unversioned source;
this leads to fetch failures when the unversioned header
is updated on the development server (upstream). The
copy tcberner@ hangs on to is also whatever-happened-to-be-
unversioned at the time the port updates.

So r547673 updated the checksum, but to whatever-was-dev
at the time, and without updating tcberner@'s distcache.
This has meant fetch-failures since then, since the
dev header has updated again.

The *previous* version of the checksum, and the copy
tcberner@ has, is actually for gmic 2.4.0.

So hit the whole dang thing with a hammer again, fetch
the versioned header, copy it into its unversioned
destination, and reset the checksum. Bump PORTREVISION
because the package -- the bundled standard library --
has changed.

Reported by: fallout