Update pyproject.toml (#3017)

needed to had a "test" not "tests" in the pyproject

pyproject.toml

@@ -60,6 +60,7 @@ dependencies = [
 tests = ["pytest", "pytest-pretty", "coverage", "scvi-tools[optional]"]
 editing = ["jupyter", "pre-commit"]
 dev = ["scvi-tools[editing,tests]"]
+test = ["scvi-tools[tests]"]
 
 docs = [
     "docutils>=0.8,!=0.18.*,!=0.19.*", # see https://github.com/scverse/cookiecutter-scverse/pull/205