chore(rds): add missing Aurora PG versions (#19811)

Closes #19803

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### Adding new Unconventional Dependencies:

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### New Features

* [ ] Have you added the new feature to an [integration test](https://github.com/aws/aws-cdk/blob/master/INTEGRATION_TESTS.md)?
	* [ ] Did you use `cdk-integ` to deploy the infrastructure and generate the snapshot (i.e. `cdk-integ` without `--dry-run`)?

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packages/@aws-cdk/aws-rds/lib/cluster-engine.ts

@@ -469,6 +469,10 @@ export class AuroraPostgresEngineVersion {
   public static readonly VER_10_16 = AuroraPostgresEngineVersion.of('10.16', '10', { s3Import: true, s3Export: true });
   /** Version "10.18". */
   public static readonly VER_10_18 = AuroraPostgresEngineVersion.of('10.18', '10', { s3Import: true, s3Export: true });
+  /** Version "10.19". */
+  public static readonly VER_10_19 = AuroraPostgresEngineVersion.of('10.19', '10', { s3Import: true, s3Export: true });
+  /** Version "10.20". */
+  public static readonly VER_10_20 = AuroraPostgresEngineVersion.of('10.20', '10', { s3Import: true, s3Export: true });
   /** Version "11.4". */
   public static readonly VER_11_4 = AuroraPostgresEngineVersion.of('11.4', '11', { s3Import: true });
   /** Version "11.6". */
@@ -483,16 +487,28 @@ export class AuroraPostgresEngineVersion {
   public static readonly VER_11_11 = AuroraPostgresEngineVersion.of('11.11', '11', { s3Import: true, s3Export: true });
   /** Version "11.13". */
   public static readonly VER_11_13 = AuroraPostgresEngineVersion.of('11.13', '11', { s3Import: true, s3Export: true });
+  /** Version "11.14". */
+  public static readonly VER_11_14 = AuroraPostgresEngineVersion.of('11.14', '11', { s3Import: true, s3Export: true });
+  /** Version "11.15". */
+  public static readonly VER_11_15 = AuroraPostgresEngineVersion.of('11.15', '11', { s3Import: true, s3Export: true });
   /** Version "12.4". */
   public static readonly VER_12_4 = AuroraPostgresEngineVersion.of('12.4', '12', { s3Import: true, s3Export: true });
   /** Version "12.6". */
   public static readonly VER_12_6 = AuroraPostgresEngineVersion.of('12.6', '12', { s3Import: true, s3Export: true });
   /** Version "12.8". */
   public static readonly VER_12_8 = AuroraPostgresEngineVersion.of('12.8', '12', { s3Import: true, s3Export: true });
+  /** Version "12.8". */
+  public static readonly VER_12_9 = AuroraPostgresEngineVersion.of('12.9', '12', { s3Import: true, s3Export: true });
+  /** Version "12.10". */
+  public static readonly VER_12_10 = AuroraPostgresEngineVersion.of('12.10', '12', { s3Import: true, s3Export: true });
   /** Version "13.3". */
   public static readonly VER_13_3 = AuroraPostgresEngineVersion.of('13.3', '13', { s3Import: true, s3Export: true });
   /** Version "13.4". */
   public static readonly VER_13_4 = AuroraPostgresEngineVersion.of('13.4', '13', { s3Import: true, s3Export: true });
+  /** Version "13.5". */
+  public static readonly VER_13_5 = AuroraPostgresEngineVersion.of('13.5', '13', { s3Import: true, s3Export: true });
+  /** Version "13.6". */
+  public static readonly VER_13_6 = AuroraPostgresEngineVersion.of('13.6', '13', { s3Import: true, s3Export: true });
 
   /**
    * Create a new AuroraPostgresEngineVersion with an arbitrary version.