Fix typing error

For an unknow reason, mypy started to generate the following error:
- src/e3/python/pypi.py:682: error: Need type annotation for reporter  [var-annotated]

So, we fix it by adding the explicitly the type.

src/e3/python/pypi.py

@@ -679,7 +679,7 @@ def _requirements_closure(self) -> dict:
             provider = PyPIProvider(
                 get_pip_env(platform, python_version=self.python3_version), self.pypi
             )
-            reporter = BaseReporter()
+            reporter: BaseReporter = BaseReporter()
             resolver: Resolver = Resolver(provider, reporter)
             try:
                 result = resolver.resolve(self.requirements, max_rounds=500)