Fix #248, change blocktype value used for custody

[jphickey]

Describe the contribution Change the custody signal blocktype from 13 to 73

Fixes #248

Testing performed Interoperability testing with remote node using different BP software

Expected behavior changes Will not conflict with custom blocktype used by remote software

System(s) tested on Debian

Contributor Info - All information REQUIRED for consideration of pull request Joseph Hickey, Vantage Systems, Inc.

[jphickey]

Reviewed and approved at 2023-09-27 CCB