idl: remove unused variables
idl: remove unused variables

This patch removes unused `parent_template_param` and `namespaces`
variables obtained from unpacking values from the `local_types` set.

Signed-off-by: Pavel Solodovnikov <2cf5887fafb117b7ff3e29b9720a7305c3313494@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla