Bump scikit-image from 0.19.3 to 0.21.0

Bumps [scikit-image](https://github.com/scikit-image/scikit-image) from 0.19.3 to 0.21.0.
- [Release notes](https://github.com/scikit-image/scikit-image/releases)
- [Changelog](https://github.com/scikit-image/scikit-image/blob/main/RELEASE.txt)
- [Commits](scikit-image/scikit-image@v0.19.3...v0.21.0)

---
updated-dependencies:
- dependency-name: scikit-image
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

setup.py

@@ -48,7 +48,7 @@
             'fenics==2019.1.0',
             'mshr==2019.1.0',
         ],
-        'image': ['scikit-image==0.19.3'],
+        'image': ['scikit-image==0.21.0'],
         'generic': [
             'boto3==1.26.142', 
             'moto==4.1.11'