New property `relationshipRef` not in `provider.definition.schema.v1.json`

Recent updates to some CloudFormation resource schemas

* AWS::ECS::Cluster
* AWS::S3::MultiRegionAccessPoint
* AWS::SSM::Association

have added a new property, `relationshipRef` , to certain properties, e.g.

```json
"Region": {
"type": "object",
"properties": {
"Bucket": {
"type": "string",
"minLength": 3,
"maxLength": 63,
"pattern": "^[a-z0-9][a-z0-9//.//-]*[a-z0-9]$",
"relationshipRef": {
"typeName": "AWS::S3::Bucket",
"propertyPath": "/properties/BucketName"
}
},
"BucketAccountId": {
"type": "string",
"minLength": 12,
"maxLength": 12,
"pattern": "^[0-9]{12}$"
}
},
"required": [
"Bucket"
],
"additionalProperties": false
}
```

This property has not been added to https://github.com/aws-cloudformation/cloudformation-resource-schema/blob/master/src/main/resources/schema/provider.definition.schema.v1.json, so validation of these resource schemas against the meta-schema are failing.

Open src/main/resources/schema/provider.definition.schema.v1.json and inspect the existing property definitions in the provider meta-schema. Add the missing relationshipRef definition implied by the examples, then validate the AWS::ECS::Cluster, AWS::S3::MultiRegionAccessPoint, and AWS::SSM::Association schemas against the meta-schema to confirm validation succeeds.

Written by the indexing model from the issue text.