[serverctl] remove broken schema-sync command
As far as I can tell the migration handler hasn't had a
cmd_synchronize_schema method since cubicweb 3.2.0.
Latest changes
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* table of `all latest changes`_
Links below is providing useful RQL query example.
.. _all latest changes: view?rql=Any+M%2CX+WHERE+X+modification_date+M+ORDERBY+M+DESC+LIMIT+30