proc: remove SLAB_MEM_SPREAD flag usage

The SLAB_MEM_SPREAD flag used to be implemented in SLAB, which was
removed as of v6.8-rc1 (see [1]), so it became a dead flag since the
commit 16a1d96 ("mm/slab: remove mm/slab.c and slab_def.h"). And
the series[1] went on to mark it obsolete explicitly to avoid confusion
for users. Here we can just remove all its users, which has no any
functional change.

Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Link: https://lore.kernel.org/all/20240223-slab-cleanup-flags-v2-1-02f1753e8303@suse.cz [1]
Link: https://lore.kernel.org/r/20240224135048.829987-1-chengming.zhou@linux.dev
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: Chengming Zhou

fs/proc/inode.c

@@ -95,7 +95,7 @@ void __init proc_init_kmemcache(void)
 	proc_inode_cachep = kmem_cache_create("proc_inode_cache",
 					     sizeof(struct proc_inode),
 					     0, (SLAB_RECLAIM_ACCOUNT|
-						SLAB_MEM_SPREAD|SLAB_ACCOUNT|
+						SLAB_ACCOUNT|
 						SLAB_PANIC),
 					     init_once);
 	pde_opener_cache =