gh-136879: Make os.spawn* arg signatures consistent with os.exec*

Update os.spawnl, spawnle, spawnlp, and spawnlpe function signatures
to show arg0, arg1, ... explicitly, matching the os.execl family of
functions for consistency.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: kovan

Doc/library/os.rst

@@ -5254,10 +5254,10 @@ written in Python, such as a mail server's external command delivery program.
    .. versionadded:: 3.7
 
 
-.. function:: spawnl(mode, path, ...)
-              spawnle(mode, path, ..., env)
-              spawnlp(mode, file, ...)
-              spawnlpe(mode, file, ..., env)
+.. function:: spawnl(mode, path, arg0, arg1, ...)
+              spawnle(mode, path, arg0, arg1, ..., env)
+              spawnlp(mode, file, arg0, arg1, ...)
+              spawnlpe(mode, file, arg0, arg1, ..., env)
               spawnv(mode, path, args)
               spawnve(mode, path, args, env)
               spawnvp(mode, file, args)