Remove redundant excludes from find_packages

Resolves #2854.

tests don't need excluded because they're not within the "src" directory.
diff --git a/setup.py b/setup.py
index 88dfd7d..d104ac3 100644
--- a/setup.py
+++ b/setup.py
@@ -302,9 +302,7 @@
     ],
 
     package_dir={"": "src"},
-    packages=find_packages(
-        where="src", exclude=["_cffi_src", "_cffi_src.*", "tests", "tests.*"]
-    ),
+    packages=find_packages(where="src", exclude=["_cffi_src", "_cffi_src.*"]),
     include_package_data=True,
 
     install_requires=requirements,