Fix reproducible build checks

[leighmcculloch]

The reproducible build check failed on the main branch after succeeding in its PR.

Main branch run that failed:

• https://github.com/stellar/go-stellar-xdr-json/actions/runs/13442470657/job/37559998368

PR run that succeeded:

• https://github.com/stellar/go-stellar-xdr-json/actions/runs/13406227300/job/37446530618