Docs: Remove duplicate word in Argument Clinic howto heading (python/cpython#107169)

Author: hakancelikdev

Doc/howto/clinic.rst

@@ -582,8 +582,8 @@ How-to guides
 =============
 
 
-How to to rename C functions and variables generated by Argument Clinic
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+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