Refactor optional dependencies in pyproject.toml and add setuptools requirement

Author: grongierisc

pyproject.toml

@@ -25,17 +25,11 @@ classifiers = [
     "Topic :: Utilities"
 ]
 
-[project.optional-dependencies]
-python_version = [
-    'importlib-metadata; python_version < "3.8"',
-    'dataclasses; python_version < "3.7"',
-    'setuptools >= 40.8.0; python_version =< "3.12"'
-]
-
 dependencies = [
     "dacite >=1.6.0",
     "xmltodict>=0.12.0",
-    "iris-embedded-python-wrapper>=0.0.6"
+    "iris-embedded-python-wrapper>=0.0.6",
+    "setuptools >= 40.8.0"
 ]
 
 license = { file = "LICENSE" }