Add breakingChanges to the removal of sigv4 and sigv4a traits

[qijuew]

Background

• The removal of sigv4 and sigv4a auth events will throw danger events since these are breaking changes
• The addition of these danger events informs the model developer to understand the significant customer impact on the auth scheme removals

Testing

• Local build passed with new unit test cases

Links

• Links to additional context, if necessary: N/A
• Issue #, if applicable: N/A

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