graphics/darktable: Update to 4.8.1

Release notes:

• https://github.com/darktable-org/darktable/releases/tag/release-4.8.0
• https://github.com/darktable-org/darktable/releases/tag/release-4.8.1

PR: 277742, 280065, 280450
Reported by: Andrew <andrew_terekhov@yahoo.com>