Update asyncio-subprocess.rst (GH-21680)

diff --git a/Doc/library/asyncio-subprocess.rst b/Doc/library/asyncio-subprocess.rst
index f955a29..ef4d9bc 100644
--- a/Doc/library/asyncio-subprocess.rst
+++ b/Doc/library/asyncio-subprocess.rst
@@ -242,7 +242,7 @@
 
    .. method:: kill()
 
-      Kill the child.
+      Kill the child process.
 
       On POSIX systems this method sends :py:data:`SIGKILL` to the child
       process.