Fix trivial typo in Python Setup documentation (GH-2185) (GH-2190)

Replace platform with platforms.
(cherry picked from commit 4ebf03d109f827c91a23256a447c1d74a203dfee)

diff --git a/Doc/using/index.rst b/Doc/using/index.rst
index 1201153daee61f12ceef689f6149ea06924e908e..96bd4b0403db5f72be215927e6a743ef09a4149e 100644 (file)
--- a/Doc/using/index.rst
+++ b/Doc/using/index.rst
@@ -6,7 +6,7 @@
 
 
 This part of the documentation is devoted to general information on the setup
-of the Python environment on different platform, the invocation of the
+of the Python environment on different platforms, the invocation of the
 interpreter and things that make working with Python easier.