Fix structure of `SEC-SIGLOG`

This PR fixes the SEC-SIGLOG message type by moving the reserved bytes into the repeated group as suggested by the interface description (Firmware version 1.40 and 1.50): https://content.u-blox.com/sites/default/files/documents/u-blox-F9-HPG-1.50_InterfaceDescription_UBXDOC-963802114-12815.pdf

Testing

I tested this change on a receiver with version 1.50

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