[3.12] Docs: Remove duplicate word in Argument Clinic howto heading (GH-107169) (#107171)

(cherry picked from commit ebe44a5)

Co-authored-by: Hakan Celik <[email protected]>

Author: miss-islington

Doc/howto/clinic.rst

@@ -582,8 +582,8 @@ 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