CfnDBCluster: Updating master_username shows replacement of resource while running cdk diff

### Describe the bug

I am creating a rds Dbcluster resource through cdk. However when i try to update the master_username property and while running the "cdk diff" command it shows that the resource requires replacement.

However i did go ahead and deployed the updated code anyway, it did update the stack but did not cause any replacement of the resource.

Is there any reason for this glitch or strange behavior?

The cdk code i used to deploy the Dbcluster resource

aurora_cluster = rds.CfnDBCluster(self, 'auroraCluster',
engine='aurora-mysql',
engine_version='5.7.mysql_aurora.2.08.1',
database_name = 'database05sep22',
master_username="masterUser",
master_user_password="masterUserPassword",
)

cdk diff output when i updated the master_username

Resources
[~] AWS::RDS::DBCluster auroraCluster auroraCluster replace
└─ [~] MasterUsername (requires replacement)
├─ [-] masterUser
└─ [+] masterUser123

### Expected Behavior

As per the cloudformation document for AWS::RDS::DBCluster the property "MasterUsername" says no interruption during update. So it should not be showing as replace while running the cdk diff command.

https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-rds-dbcluster.html#cfn-rds-dbcluster-masterusername

### Current Behavior

While running the cdk diff command I get resource replace message when i change the master_username property

[~] AWS::RDS::DBCluster auroraCluster auroraCluster replace
└─ [~] MasterUsername (requires replacement)
├─ [-] masterUser
└─ [+] masterUser123

### Reproduction Steps

It is a python code
=======================
aurora_cluster = rds.CfnDBCluster(self, 'auroraCluster',
engine='aurora-mysql',
engine_version='5.7.mysql_aurora.2.08.1',
database_name = 'database05sep22',
master_username="masterUser123",
master_user_password="masterUserPassword",)
========================

### Possible Solution

_No response_

### Additional Information/Context

_No response_

### CDK CLI Version

2.31.0 (build b67950d)

### Framework Version

_No response_

### Node.js Version

8.12.1

### OS

MAC

### Language

Python

### Language Version

_No response_

### Other information

_No response_

Start by reproducing the Python AWS::RDS::DBCluster example with the CDK CLI version 2.31.0 and compare the cdk diff output for MasterUsername with the CloudFormation documentation linked in the issue. Check whether the diff's replacement classification matches the documented no-interruption update behavior; done means the diff no longer reports replacement when only master_username changes.

Written by the indexing model from the issue text.