[doc] Fix padding in timeit (GH-22152)


Compare -p and -u options help in rendered output to see the difference.
(cherry picked from commit 594f0ce73be807c0fecf958dc0644fa37983f5fe)

Co-authored-by: Andre Delfino <adelfino@gmail.com>
diff --git a/Doc/library/timeit.rst b/Doc/library/timeit.rst
index 46fa62c..668fcb8 100644
--- a/Doc/library/timeit.rst
+++ b/Doc/library/timeit.rst
@@ -233,7 +233,7 @@
 
 .. cmdoption:: -u, --unit=U
 
-    specify a time unit for timer output; can select nsec, usec, msec, or sec
+   specify a time unit for timer output; can select nsec, usec, msec, or sec
 
    .. versionadded:: 3.5