fix: update docstring to match type hint (googleapis#172)

* fix: update docstring to match type hint

* proto/modules.py

* Update modules.py

Co-authored-by: Dov Shlachter <dovs@google.com>

Author: 0x2b3bfa0

proto/modules.py

@@ -33,7 +33,7 @@ def define_module(
         package (str): The proto package name.
         marshal (str): The name of the marshal to use. It is recommended
             to use one marshal per Python library (e.g. package on PyPI).
-        manifest (Tuple[str]): A tuple of classes to be created. Setting
+        manifest (Set[str]): A set of messages and enums to be created. Setting
             this adds a slight efficiency in piecing together proto
             descriptors under the hood.
     """