eclass-overlay: fix comments in preserve group

BUG=None
TEST=./build_image

Change-Id: Ic815ecf4ee4dd0a8445019fcec8e50c2c1930341
Reviewed-on: https://chromium-review.googlesource.com/1582360
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Leo Lai <cylai@google.com>
Reviewed-by: John  Chen <zuan@chromium.org>
Reviewed-by: Wei-Cheng Xiao <garryxiao@chromium.org>
diff --git a/profiles/base/accounts/group/preserve b/profiles/base/accounts/group/preserve
index ec0ab23..4ccc20a 100644
--- a/profiles/base/accounts/group/preserve
+++ b/profiles/base/accounts/group/preserve
@@ -1,4 +1,5 @@
 group:preserve
 gid:253
-# Only certain users are allowed to write to /mnt/stateful/unencrypted/preserve.
+# only these users are allowed to write to
+# /mnt/stateful_partition/unencrypted/preserve.
 users:root,attestation,tpm_manager