CfnMapping: Error when deploying template with mapping default value

### Describe the bug

When attempting to deploy a stack that was successfully synthesized using the following code:
```
self.add_transform("AWS::LanguageExtensions")

...

ipset_mapping = CfnMapping(
self,
"IpSetMapping",
mapping={
"us-east-1": {
"Beta": "arn:aws:wafv2:us-east-1::regional/ipset/Beta-NatGateway-IPs/a2d011ef-1756-4563-9466-ad5615420c45",
"Preview": "arn:aws:wafv2:us-east-1::regional/ipset/Preview-NatGateway-IPs/db157747-175a-40ae-b780-d2e8cb6af7f4",
"Prod": "arn:aws:wafv2:us-east-1::regional/ipset/Prod-NatGateway-IPs/39b48ae3-d224-4bc3-87cf-c6827ce15d5d",
},
"ca-central-1": {
"Prod": "arn:aws:wafv2:ca-central-1::regional/ipset/Prod-NatGateway-IPs/4523362c-c473-4e8b-8068-cb3a2dadb0bd",
},
"eu-central-1": {
"Prod": "arn:aws:wafv2:eu-central-1::regional/ipset/Prod-NatGateway-IPs/fdb0fdfe-e479-4216-be04-bfafa9cc329b",
},
"ap-southeast-2": {
"Prod": "arn:aws:wafv2:ap-southeast-2::regional/ipset/Prod-NatGateway-IPs/c07a88f7-1b9b-4e1c-97e0-07a4c711631e"
},
},
)

...

ip_set_scope_down_statement = wafv2.CfnWebACL.StatementProperty(
not_statement=wafv2.CfnWebACL.NotStatementProperty(
statement=wafv2.CfnWebACL.StatementProperty(
ip_set_reference_statement=wafv2.CfnWebACL.IPSetReferenceStatementProperty(
arn=ipset_mapping.find_in_map(
Fn.sub("${AWS::Region}"),
environment.value_as_string,
"arn:aws:wafv2:us-east-1::regional/ipset/Beta-NatGateway-IPs/a2d011ef-1756-4563-9466-ad5615420c45",
)
)
)
)
)
```

The synthesized template shows:
```

"Transform": [
"AWS::LanguageExtensions"
],

...

"Mappings": {
"IpSetMapping": {
"us-east-1": {
"Beta": "arn:aws:wafv2:us-east-1::regional/ipset/Beta-NatGateway-IPs/a2d011ef-1756-4563-9466-ad5615420c45",
"Preview": "arn:aws:wafv2:us-east-1::regional/ipset/Preview-NatGateway-IPs/db157747-175a-40ae-b780-d2e8cb6af7f4",
"Prod": "arn:aws:wafv2:us-east-1::regional/ipset/Prod-NatGateway-IPs/39b48ae3-d224-4bc3-87cf-c6827ce15d5d"
},
"ca-central-1": {
"Prod": "arn:aws:wafv2:ca-central-1::regional/ipset/Prod-NatGateway-IPs/4523362c-c473-4e8b-8068-cb3a2dadb0bd"
},
"eu-central-1": {
"Prod": "arn:aws:wafv2:eu-central-1::regional/ipset/Prod-NatGateway-IPs/fdb0fdfe-e479-4216-be04-bfafa9cc329b"
},
"ap-southeast-2": {
"Prod": "arn:aws:wafv2:ap-southeast-2::regional/ipset/Prod-NatGateway-IPs/c07a88f7-1b9b-4e1c-97e0-07a4c711631e"
}
}
},

...

"scopeDownStatement": {
"notStatement": {
"statement": {
"ipSetReferenceStatement": {
"arn": {
"Fn::FindInMap": [
"IpSetMapping",
{
"Fn::Sub": "${AWS::Region}"
},
{
"Ref": "Environment"
},
{
"DefaultValue": "arn:aws:wafv2:us-east-1::regional/ipset/Beta-NatGateway-IPs/a2d011ef-1756-4563-9466-ad5615420c45"
}
]
}
}
}
}
}
```

The change set validation/stack deployment fails with `Template error: every Fn::FindInMap object requires three parameters, the map name, map key and the attribute for return value.`

I have also tried adding the map name:

```
ipset_mapping.find_in_map(
"IpSetMapping",
Fn.sub("${AWS::Region}"),
environment.value_as_string,
"arn:aws:wafv2:us-east-1::regional/ipset/Beta-NatGateway-IPs/a2d011ef-1756-4563-9466-ad5615420c45",
)
```

According to the [documentation](https://docs.aws.amazon.com/cdk/api/v2/python/aws_cdk/CfnMapping.html#aws_cdk.CfnMapping.find_in_map) my code appears to be correct.

### Expected Behavior

The synthesized stack deploys successfully.

### Current Behavior

The change set validation/stack deployment fails with `Template error: every Fn::FindInMap object requires three parameters, the map name, map key and the attribute for return value.`

### Reproduction Steps

Synthesize and attempt to deploy a template using code similar to:

```
ipset_mapping.find_in_map(
Fn.sub("${AWS::Region}"),
environment.value_as_string,
"arn:aws:wafv2:us-east-1::regional/ipset/Beta-NatGateway-IPs/a2d011ef-1756-4563-9466-ad5615420c45",
)
```

### Possible Solution

_No response_

### Additional Information/Context

_No response_

### CDK CLI Version

2.115.0 (build 58027ee)

### Framework Version

_No response_

### Node.js Version

21.4.0

### OS

MacOS

### Language

Python

### Language Version

3.12.0

### Other information

_No response_

Start at the CfnMapping.find_in_map entry point and inspect how the Python call is rendered into the synthesized Fn::FindInMap object. Reproduce the template from the issue and validate it through a change set or deployment, focusing on the extra default-value parameter. Done means the synthesized mapping is accepted and the stack deploys successfully.

Written by the indexing model from the issue text.