ext4: correct comment of ext4_xattr_block_cache_insert

There is no return value from ext4_xattr_block_cache_insert, just correct
it's comment about return value.
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://patch.msgid.link/20240606125508.1459893-3-shikemeng@huaweicloud.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/xattr.c

@@ -3036,8 +3036,6 @@ void ext4_xattr_inode_array_free(struct ext4_xattr_inode_array *ea_inode_array)
  *
  * Create a new entry in the extended attribute block cache, and insert
  * it unless such an entry is already in the cache.
- *
- * Returns 0, or a negative error number on failure.
  */
 static void
 ext4_xattr_block_cache_insert(struct mb_cache *ea_block_cache,