Fix a couple documentation typos. (GH-10498)



reproduciblity -> reproducibility
PyPA are the group -> PyPA is the group
diff --git a/Doc/installing/index.rst b/Doc/installing/index.rst
index 8f105a1..747b9223 100644
--- a/Doc/installing/index.rst
+++ b/Doc/installing/index.rst
@@ -48,7 +48,7 @@
   repository of open source licensed packages made available for use by
   other Python users.
 * the `Python Packaging Authority
-  <https://www.pypa.io/>`__ are the group of
+  <https://www.pypa.io/>`__ is the group of
   developers and documentation authors responsible for the maintenance and
   evolution of the standard packaging tools and the associated metadata and
   file format standards. They maintain a variety of tools, documentation,