Bump graphviz from 0.20.3 to 0.21 (#123)

Bumps [graphviz](https://github.com/xflr6/graphviz) from 0.20.3 to 0.21.
- [Changelog](https://github.com/xflr6/graphviz/blob/master/CHANGES.rst)
- [Commits](xflr6/graphviz@0.20.3...0.21)

---
updated-dependencies:
- dependency-name: graphviz
  dependency-version: '0.21'
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

poetry.lock

@@ -25,7 +25,7 @@ pyreadr = "0.5.4" # read R data files
 types-psutil = "6.1.0.20241102" # type hints for psutil
 psutil = "7.2.2" # process and system utilities
 torchview = "0.2.6" # model visualization library
-graphviz = "0.20.3" # graph visualization library
+graphviz = "0.21" # graph visualization library
 matplotlib = "3.10.0" # plotting library
 pillow = "12.1.1" # image processing library
 torchvision ="0.26" # computer vision library