The default RRC reconfiguration was previously sent after the security
mode command as a "first" RRC reconfiguration. However, it is simply not
needed, as it will be triggered through a subsequent reconfiguration
that also sets up DRBs.

Move the Measurement Config to the "other/dedicated" RRC
reconfiguration.

This reconfiguration would have forwarded a NAS PDU (typically a
registration accept). This is now done by a dedicated forwarding of NAS.