lint: remove namespace package config (#14024)

Author: miketheman

pyproject.toml

@@ -11,7 +11,6 @@ known_first_party = ['warehouse', 'tests']
 
 [tool.mypy]
 python_version = "3.11"
-namespace_packages = true
 warn_unused_configs = true
 # Plugin order matters. `mypy_zope` must come before `sqlalchemy` to prevent
 # false-positive signature mismatch errors for `zope.interface` instances.