Cannot be done. Databases can never be downgraded.
For log shipping with standby, the secondary must be the same version as the primary. If you're restoring with norecovery, the secondary can be a higher version, but never a lower.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability