Conflict contract tests: contract_update_non_existent_resource and contract_update_create_only_property

Hey,

Our team is failing with contract test contract_update_non_existent_resource due it use contract_update_create_only_property test json file as previous resource model. This will make a failure loop that:

If test update the resource with same resource name, contract_update_create_only_property will failed due there is no createonly property change.

if test update the resource with different resource name, contract_update_non_existent_resource will failed due `CfnNotUpdatableException` instead of NotFound.

Let me know if you wanna me clarify something, thanks!
Alex