docs(rds): fix weird rendering of socketAddress property in Endpoint (#13125)

Based the fix on
[`domainName` in `CertificateProps`](https://github.com/aws/aws-cdk/blob/33339e1c5f3ac280018e294c268c68929707dcce/packages/%40aws-cdk/aws-certificatemanager/lib/certificate.ts#L28-L28)
(rendered version: https://docs.aws.amazon.com/cdk/api/latest/python/aws_cdk.aws_certificatemanager/CertificateProps.html#aws_cdk.aws_certificatemanager.CertificateProps.domain_name).

Fixes #12287


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Author: skinny85

packages/@aws-cdk/aws-docdb/lib/endpoint.ts

@@ -40,7 +40,7 @@ export class Endpoint {
   public readonly port: number;
 
   /**
-   * The combination of "HOSTNAME:PORT" for this endpoint
+   * The combination of ``HOSTNAME:PORT`` for this endpoint.
    */
   public readonly socketAddress: string;