Add notes for bumping version as part of a release (#27080)
### Description
<!-- Describe your changes. -->
When creating a release branch for a new ORT release, there are some
steps required to comprehensively update the version number across the
codebase. This change adds the steps for that for anyone driving a
release.
### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->
This will help with the release process and ensure that any bits
produced from release branches carry the right version information.
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Co-authored-by: Aditya Rastogi <adityar@ntdev.microsoft.com>
