Docs: Remove duplicate word in Argument Clinic howto heading (pythonG…

…H-107169)

(cherry picked from commit ebe44a5)

Co-authored-by: Hakan Celik <hakancelikdev@gmail.com>

Doc/howto/clinic.rst

@@ -574,8 +574,8 @@ How-to guides
 =============
 
 
-How to to rename C functions and variables generated by Argument Clinic
------------------------------------------------------------------------
+How to rename C functions and variables generated by Argument Clinic
+--------------------------------------------------------------------
 
 Argument Clinic automatically names the functions it generates for you.
 Occasionally this may cause a problem, if the generated name collides with