make antlr optional dependency

pyproject.toml

@@ -5,15 +5,16 @@ authors = [{name = "Substrait contributors", email = "[email protected]
 license = {text = "Apache-2.0"}
 readme = "README.md"
 requires-python = ">=3.8.1"
-dependencies = ["protobuf >= 3.20", "antlr4-python3-runtime"]
+dependencies = ["protobuf >= 3.20"]
 dynamic = ["version"]
 
 [tool.setuptools_scm]
 write_to = "src/substrait/_version.py"
 
 [project.optional-dependencies]
+extensions = ["antlr4-python3-runtime"]
 gen_proto = ["protobuf == 3.20.1", "protoletariat >= 2.0.0"]
-test = ["pytest >= 7.0.0"]
+test = ["pytest >= 7.0.0", "antlr4-python3-runtime"]
 
 [tool.pytest.ini_options]
 pythonpath = "src"