nixos/syncoid: avoid leaking zfs list into journald log (#473450)

nixos/modules/services/backup/syncoid.nix

@@ -27,7 +27,7 @@ let
   # Function to build "zfs allow" commands for the filesystems we've delegated
   # permissions to. It also checks if the target dataset exists before
   # delegating permissions, if it doesn't exist we delegate it to the parent
-  # dataset (if it exists). This should solve the case of provisoning new
+  # dataset (if it exists). This should solve the case of provisioning new
   # datasets.
   buildAllowCommand =
     permissions: dataset:
@@ -42,7 +42,7 @@ let
           "list"
           dataset
         ]
-      } 2> /dev/null; then
+      } 2>&1 >/dev/null; then
         ${lib.escapeShellArgs [
           "/run/booted-system/sw/bin/zfs"
           "allow"