selftests: cgroup: remove redundant enabling of memory controller

Memory controller is already enabled in main which invokes the test, hence
this does not need to be done in test_no_kmem_bypass.

Link: https://lkml.kernel.org/r/20240502200529.4193651-2-usamaarif642@gmail.com
Signed-off-by: Usama Arif <usamaarif642@gmail.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>