mm: fix typo in Kconfig

mm: fix typo in Kconfig

Fix typo in Kconfig help

Link: https://lkml.kernel.org/r/78656.1720853990@turing-police
Fixes: e93d4166b40a ("mm: memcg: put cgroup v1-specific code under a config option")
Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>