[doc] Fix typo in os module (GH-24464)

Automerge-Triggered-By: GH:iritkatriel
(cherry picked from commit fdc7e52)

Co-authored-by: Rafael Fontenelle <[email protected]>

Author: miss-islington

Doc/library/os.rst

@@ -4635,7 +4635,7 @@ operating system.
 
 .. function:: sched_setparam(pid, param)
 
-   Set a scheduling parameters for the process with PID *pid*. A *pid* of 0 means
+   Set the scheduling parameters for the process with PID *pid*. A *pid* of 0 means
    the calling process. *param* is a :class:`sched_param` instance.