Issue #25127: Fix typo in concurrent.futures.rst
Reported by Jakub Wilk.
diff --git a/Doc/library/concurrent.futures.rst b/Doc/library/concurrent.futures.rst
index 48b4362..cc8b335 100644
--- a/Doc/library/concurrent.futures.rst
+++ b/Doc/library/concurrent.futures.rst
@@ -75,7 +75,7 @@
e.submit(shutil.copy, 'src1.txt', 'dest1.txt')
e.submit(shutil.copy, 'src2.txt', 'dest2.txt')
e.submit(shutil.copy, 'src3.txt', 'dest3.txt')
- e.submit(shutil.copy, 'src3.txt', 'dest4.txt')
+ e.submit(shutil.copy, 'src4.txt', 'dest4.txt')
ThreadPoolExecutor