Add missing levels to constraints

[Gabeblis]

Committer Notes

Purpose

This PR aims to add the missing @level attribute to several constraints in the fedramp-external-constraints.xml file.

Changes

• Added level="ERROR" to constraints that were missing the @level attribute.

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  - [ ] If applicable, have all FedRAMP Documents Related to OSCAL Adoption affected by the changes in this issue have been updated.? No documentation is needed for this change as it is a minor correction to a file.
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[aj-stein-gsa]

Interesting, thanks for the catch.