ext4: call deactivate_super() in extents_kunit_exit()

Call deactivate_super() is called in extents_kunit_exit() to cleanup
the file system resource.

Fixes: cb1e0c1 ("ext4: kunit tests for extent splitting and conversion")
Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://patch.msgid.link/20260330133035.287842-3-yebin@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: Ye Bin

fs/ext4/extents-test.c

@@ -146,6 +146,7 @@ static void extents_kunit_exit(struct kunit *test)
 	struct ext4_sb_info *sbi = sb->s_fs_info;
 
 	ext4_es_unregister_shrinker(sbi);
+	deactivate_super(sbi->s_sb);
 	kfree(sbi);
 	kfree(k_ctx.k_ei);
 	kfree(k_ctx.k_data);