aws-s3-deployment: SourceMarkers contains duplicates

### Describe the bug

if same deploy-time value used more then once, produced template conteans duplicates of corresponding marker.
does not affects the functionality,

### Expected Behavior

each distinct marker generated only once

### Current Behavior

duplicates are present:
```
...
"SourceMarkers": [
{
"<>": {
"Fn::GetAtt": [
"testBucketDF4D7D1A",
"DomainName"
]
},
"<>": {
"Fn::GetAtt": [
"testBucketDF4D7D1A",
"RegionalDomainName"
]
}
},
{
"<>": {
"Fn::GetAtt": [
"testBucketDF4D7D1A",
"DomainName"
]
},
"<>": {
"Fn::GetAtt": [
"testBucketDF4D7D1A",
"RegionalDomainName"
]
}
}
],
...
```

### Reproduction Steps

```
@Getter
@ToString
public class Stack2 extends Stack {

private final BucketDeployment dwcWebDeployment;

@SneakyThrows
@lombok.Builder
Stack2(
@NonNull Construct scope,
@NonNull StackProps props,
@NonNull Stack1 stack1
) {
super(scope, "Stack2", props);

Bucket testBucket = Bucket.Builder.create(this, "testBucket").build();

WebConfig webConfig = WebConfig.builder()
.hostUrl(testBucket.getBucketDomainName())
.s3HostUrl(testBucket.getBucketRegionalDomainName() )
.build();

dwcWebDeployment = BucketDeployment.Builder.create(this, "deployment")
.destinationBucket(testBucket)
.logRetention(RetentionDays.ONE_MONTH)
.sources(asList(
Source.jsonData("config.json", webConfig),
Source.jsonData("config2.json", webConfig)
))
.build();
}

@lombok.Builder
@Data
@AllArgsConstructor
@NoArgsConstructor
public static class WebConfig {

@NonNull String hostUrl;
@NonNull String s3HostUrl;
}

}

```

### Possible Solution

_No response_

### Additional Information/Context

_No response_

### CDK CLI Version

2.27.0 (build 8e89048)

### Framework Version

_No response_

### Node.js Version

v18.7.0

### OS

Windows 10

### Language

Java

### Language Version

_No response_

### Other information

_No response_

Start in the aws-s3-deployment marker-generation path, using the Stack2 reproduction with two Source.jsonData inputs that reuse WebConfig. Synthesize the template and inspect SourceMarkers; done means each distinct marker appears only once while deployment behavior remains unchanged.

Written by the indexing model from the issue text.