nilfs2: modify list of unsupported features in caveats

This clarifies missing features of nilfs as a regular filesystem.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

Documentation/filesystems/nilfs2.txt

@@ -39,9 +39,8 @@ Features which NILFS2 does not support yet:
 	- extended attributes
 	- POSIX ACLs
 	- quotas
-	- writable snapshots
-	- remote backup (CDP)
-	- data integrity
+	- fsck
+	- resize
 	- defragmentation
 
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