fix: don't package tests (#193)

caused by googleapis/python-resource-manager@8fa2ec4

Apoligies if I'm missing something: I'm not entirely sure why the local packages/namespaces are still being generated but then discarded for the actual `setuptools.setup`.

Co-authored-by: Anthonios Partheniou <partheniou@google.com>

Author: s22chan

packages/google-cloud-resource-manager/setup.py

@@ -61,7 +61,7 @@
     author_email="googleapis-packages@google.com",
     license="Apache 2.0",
     url=url,
-    packages=setuptools.PEP420PackageFinder.find(),
+    packages=packages,
     namespace_packages=("google", "google.cloud"),
     platforms="Posix; MacOS X; Windows",
     include_package_data=True,