docs(s3): remove vestigial documentation (aws#18604)

fixes aws#18575 
Models documentation for [similar](https://docs.aws.amazon.com/cdk/api/v1/docs/@aws-cdk_aws-ec2.VpcAttributes.html) [structs](https://docs.aws.amazon.com/cdk/api/v1/docs/@aws-cdk_aws-lambda.FunctionAttributes.html)

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packages/@aws-cdk/aws-s3/lib/bucket.ts

@@ -356,9 +356,7 @@ export interface IBucket extends IResource {
 }
 
 /**
- * A reference to a bucket. The easiest way to instantiate is to call
- * `bucket.export()`. Then, the consumer can use `Bucket.import(this, ref)` and
- * get a `Bucket`.
+ * A reference to a bucket outside this stack
  */
 export interface BucketAttributes {
   /**