fix instances of consecutive articles (closes #23221)

Patch by Karan Goel.
diff --git a/Lib/distutils/dir_util.py b/Lib/distutils/dir_util.py
index e2dc6f4..f90318e 100644
--- a/Lib/distutils/dir_util.py
+++ b/Lib/distutils/dir_util.py
@@ -83,7 +83,7 @@
     """Create all the empty directories under 'base_dir' needed to put 'files'
     there.
 
-    'base_dir' is just the a name of a directory which doesn't necessarily
+    'base_dir' is just the name of a directory which doesn't necessarily
     exist yet; 'files' is a list of filenames to be interpreted relative to
     'base_dir'.  'base_dir' + the directory portion of every file in 'files'
     will be created if it doesn't already exist.  'mode', 'verbose' and