doc: Update SHA256SUMS.asc step in release-process.md
doc: Update SHA256SUMS.asc step in release-process.md

- The Hash: header is prepended by gpg, and states the hashing used by
  gpg, not what is used to hash the files

- Add more detailed steps

syscoin/syscoin,syscoin/syscoin,domob1812/crowncoin,domob1812/crowncoin,domob1812/crowncoin,Infernoman/crowncoin,syscoin/syscoin,domob1812/crowncoin,Infernoman/crowncoin,Crowndev/crowncoin,Crowndev/crowncoin,Infernoman/crowncoin,Crowndev/crowncoin,domob1812/crowncoin,Infernoman/crowncoin,Crowndev/crowncoin,syscoin/syscoin,Infernoman/crowncoin,Infernoman/crowncoin,syscoin/syscoin,Crowndev/crowncoin,syscoin/syscoin,Crowndev/crowncoin,syscoin/syscoin,syscoin/syscoin,domob1812/crowncoin