Remove redundant wheel dep from pyproject.toml

Remove the redundant `wheel` dependency, as it is added by the backend
automatically.  Listing it explicitly in the documentation was
a historical mistake and has been fixed since, see:
f7d30a9529

pyproject.toml

@@ -1,5 +1,5 @@
 [build-system]
-requires = ["setuptools >= 40.6.0", "wheel"]
+requires = ["setuptools >= 40.6.0"]
 build-backend = "setuptools.build_meta"
 
 [tool.black]