chore(rds): add AuroraMysqlEngineVersion 2.10.3 (#22860)

Aurora MySQL 2.10.3 is generally available, but is not supported by aws-cdk.
[Aurora MySQL database engine updates 2022-11-01 (version 2.10.3) - Amazon Aurora](https://docs.aws.amazon.com/AmazonRDS/latest/AuroraMySQLReleaseNotes/AuroraMySQL.Updates.2103.html)

I've added the engine version, just as has done previously like #19040

----

### All Submissions:

* [x] Have you followed the guidelines in our [Contributing guide?](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md)

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

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

@@ -410,6 +410,8 @@ export class AuroraMysqlEngineVersion {
   public static readonly VER_2_10_1 = AuroraMysqlEngineVersion.builtIn_5_7('2.10.1');
   /** Version "5.7.mysql_aurora.2.10.2". */
   public static readonly VER_2_10_2 = AuroraMysqlEngineVersion.builtIn_5_7('2.10.2');
+  /** Version "5.7.mysql_aurora.2.10.3". */
+  public static readonly VER_2_10_3 = AuroraMysqlEngineVersion.builtIn_5_7('2.10.3');
   /** Version "8.0.mysql_aurora.3.01.0". */
   public static readonly VER_3_01_0 = AuroraMysqlEngineVersion.builtIn_8_0('3.01.0');
   /** Version "8.0.mysql_aurora.3.01.1". */