Update graphviz requirement from <0.19,>=0.14 to >=0.14,<0.20

Updates the requirements on [graphviz](https://github.com/xflr6/graphviz) to permit the latest version.
- [Release notes](https://github.com/xflr6/graphviz/releases)
- [Changelog](https://github.com/xflr6/graphviz/blob/master/CHANGES.rst)
- [Commits](xflr6/graphviz@0.14...0.19)

---
updated-dependencies:
- dependency-name: graphviz
  dependency-type: direct:production
...

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

setup.py

@@ -27,7 +27,7 @@ def read(*parts):
 
 install_requires = [
     "click>=7.1,<8.1",
-    "graphviz>=0.14,<0.19",
+    "graphviz>=0.14,<0.20",
     "protobuf>=3.13,<3.20"
 ]