Bump colorgrad from 0.6.2 to 0.7.0

Bumps [colorgrad](https://github.com/mazznoer/colorgrad-rs) from 0.6.2 to 0.7.0.
- [Release notes](https://github.com/mazznoer/colorgrad-rs/releases)
- [Changelog](https://github.com/mazznoer/colorgrad-rs/blob/master/CHANGELOG.md)
- [Commits](mazznoer/colorgrad-rs@v0.6.2...v0.7.0)

---
updated-dependencies:
- dependency-name: colorgrad
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Cargo.lock

@@ -49,7 +49,7 @@ glob = { version = "0.3.1", optional = true }
 polars = { version = "0.41.3", optional = true, default-features = false, features = ["csv", "lazy", "fmt", "polars-ops", "asof_join", "ndarray"] }
 plotters = { version = "0.3.6", optional = true }
 itertools = { version = "0.13.0", optional = true }
-colorgrad = { version = "0.6.2", optional = true }
+colorgrad = { version = "0.7.0", optional = true }
 ndarray = { version = "0.16.0", optional = true }
 ndarray-stats = { version = "0.5.1", optional = true }