fix(autoscale): Fix when making CFN update, an autoscaled instance should not fail the CFN deploy

[angusy29]

Issue #, if available:
aws-cloudformation/cloudformation-coverage-roadmap#430

Description of changes:

When an instance is autoscaled out, the template no longer matches the real instance's AllocatedStorage.

For example:

Given a template:

Resource:
  DBInstance:
    Type: AWS::RDS::DBInstance
      AllocatedStorage: 100
      MaxAllocatedStorage: 500

When the DBInstance reaches high storage utilization, it scales from AllocatedStorage 100 => AllocatedStorage 120

On template update, the ModifyDBInstance call, for ProvisionedIOPS volumes (gp3/io1/io2), will pass the template's AllocatedStorage into the ModifyDBInstance call.

This surfaces as an exception similar to:

Resource handler returned message: "Invalid storage size for engine name mysql and storage type gp3: 100 (Service: Rds, Status Code: 400, Request ID: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx)" (RequestToken: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx, HandlerErrorCode: InvalidRequest)

This PR ensures that on template update, the CloudFormation stack on update will succeed despite the autoscaled out instance.

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