Correct grammar in concurrent/futures/process.py docstring (GH-12761)

diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py
index 306e9ce..e6ce278 100644
--- a/Lib/concurrent/futures/process.py
+++ b/Lib/concurrent/futures/process.py
@@ -3,7 +3,7 @@
 
 """Implements ProcessPoolExecutor.
 
-The follow diagram and text describe the data-flow through the system:
+The following diagram and text describe the data-flow through the system:
 
 |======================= In-process =====================|== Out-of-process ==|