Add visualization optional dependency for graphviz

Author: MartinEBravo

pyproject.toml

@@ -34,6 +34,7 @@ Repository = "https://github.com/openai/openai-agents-python"
 
 [project.optional-dependencies]
 voice = ["numpy>=2.2.0, <3; python_version>='3.10'", "websockets>=15.0, <16"]
+visualization = ["graphviz>=0.17"]
 
 [dependency-groups]
 dev = [
@@ -57,11 +58,6 @@ dev = [
     "websockets",
 ]
 
-[project.optional-dependencies]
-visualization = [
-    "graphviz>=0.17",
-]
-
 [tool.uv.workspace]
 members = ["agents"]