docs: cgroup-v1: fix typo

"listers" -> "listeners"

Signed-off-by: Xiongwei Song <xiongwei.song@windriver.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

Author: Xiongwei Song

Documentation/admin-guide/cgroup-v1/memory.rst

@@ -909,7 +909,7 @@ experiences some pressure. In this situation, only group C will receive the
 notification, i.e. groups A and B will not receive it. This is done to avoid
 excessive "broadcasting" of messages, which disturbs the system and which is
 especially bad if we are low on memory or thrashing. Group B, will receive
-notification only if there are no event listers for group C.
+notification only if there are no event listeners for group C.
 
 There are three optional modes that specify different propagation behavior: