graphics/wallust: update to 2.7.1

Changes from 2.7.0 (won't have a release)

- new colorspace: labfast, ignores floating points to be faster at the
- cost of precision
- new backend: fastresize, uses SIMD methods but it fails (for some
  reason) on some images in which usual resized doesn't.
- new flag: -T/--skip_templates
- improve overall colorpsaces (lab, labmixed) (74184f0de5)
    - Default to delta_1994 allowing faster runtimes (e0549c1afb)
    - Make the darkest and lighest value 0.3 times the threshold,
      much more better color selection, avoiding plain dark or
      white ones
    - Use generics to encourage more colorspaces
- add some benches
- update dependencies (aae66574fa)
- Config File: Now it's allowed using lab-mixed or labmixed (same
  with hard-dark, fast-resize and other two word methods)
- overall code improvements (refactors, PathBuf instead of String,
  slices over &Vec<>, ..)

(pin)