fix: reserved instances, aurora rds specifics @oycyc (#249)
## what RDS Reserved Instances multi AZ mode is never available for Aurora engines, see images on the console - this PR checks to ensure that it is set to false if the engine is Aurora:  why
That configuration isn't really applicable anyways since this statement from the AWS docs https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/USER_WorkingWithReservedDBInstances.html:
references
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