Revert "Adjust dependency group structure"

Dev-dependencies that will never be shipped with this package should be
in [dependency-groups].

Author: ThyMYthOS

pyproject.toml

@@ -26,7 +26,8 @@ dependencies = [
 requires = ["hatchling>=1.27.0"]
 build-backend = "hatchling.build"
 
-[project.optional-dependencies]
+
+[dependency-groups]
 dev = [
     "jinja2>=3.1.6",
     "pytest>=8.3.5",