Fix formatting in release-process.md

Summary: Indent sub-point on the bulleted list

Test Plan: I previewed the change in Github to see that it rendered properly

Reviewers: jasonbcox, deadalnix, #bitcoin_abc

Reviewed By: jasonbcox, #bitcoin_abc

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2509