The "IsDeleted" column is required for data changes tracking when using synchronization or replication (incremental updates).
The RecordType object doesn't have the "IsDeleted" column and, due to the fact that this is a system column, it cannot be created manually. Thus, the error you are getting while trying to create sync task is an expected one.
If you are interested in a one-way integration from Salesforce to PostgreSQL database, you can use Replication package without Incremental Updates option.
For this select only "Drop Tables" and "Create Tables" check boxes for replicating such objects. In this case, the necessary database tables will be recreated each time the package is running.
If you have any further questions, feel free to contact us.