Add ADR to formally deprecate Spock versioning, formalize Semantic Versioning Use

[aj-stein-gsa]

Committer Notes

This is a PR to backport a previously made decision in previous implementer meetings in the Automation Team. We need to complete this as part of #847, along with website documentation, to properly inform the requirements in #833.

All Submissions:

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• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Have you squashed any non-relevant commits and commit messages? [instructions] To be complete before merge.
• Have you added an explanation of what your changes do and why you'd like us to include them?
• If applicable, have all FedRAMP Documents Related to OSCAL Adoption affected by the changes in this issue have been updated? Pending in Correct and update align release guidance automate.fedramp.gov#104.
• If applicable, does this PR reference the issue it addresses and explain how it addresses the issue?

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[Rene2mt]

@aj-stein-gsa looks good overall. Just a couple of minor suggestions.