Remove build deps: setuptools, setuptools-scm

`setuptools` and `setuptools-scm` were listed as build dependencies
in `pyproject.toml`'s  `build-system.requires`.
But this was non-sense, since the build backend is `poetry-core`.

pyproject.toml

@@ -76,7 +76,7 @@ exclude = '''
 '''
 
 [build-system]
-requires = ["poetry-core>=1.0.0", "setuptools>=45", "setuptools_scm[toml]>=6.2"]
+requires = ["poetry-core>=1.0.0"]
 build-backend = "poetry.core.masonry.api"
 
 [tool.poetry.scripts]