Bump graphviz from 0.20.1 to 0.20.3

Bumps [graphviz](https://github.com/xflr6/graphviz) from 0.20.1 to 0.20.3.
- [Changelog](https://github.com/xflr6/graphviz/blob/master/CHANGES.rst)
- [Commits](xflr6/graphviz@0.20.1...0.20.3)

---
updated-dependencies:
- dependency-name: graphviz
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

docs/requirements.txt

@@ -8,7 +8,7 @@ numpy==1.24.3
 numpydoc==1.5.0
 astropy==5.3.1
 pydot==2.0.0
-graphviz==0.20.1
+graphviz==0.20.3
 astroquery==0.4.6
 boto3==1.28.7
 plotly==5.20.0