gh-39482: fix one typo
    
just a little typo

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- [x] The title is concise and informative.
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preview.
    
URL: #39482
Reported by: Frédéric Chapoton
Reviewer(s): camille-garnier

Author: Release Manager

src/sage/graphs/cographs.py

@@ -395,7 +395,7 @@ def change_label(tree, status, counter):
 
     - ``tree`` -- the tree to relabel
 
-    - ``status`` -- boolean; used to to detect series (``True``) and parallel
+    - ``status`` -- boolean; used to detect series (``True``) and parallel
       (``False``) internal nodes
 
     - ``counter`` -- list; the first integer of the list is used to assign a