chore(rds): add new AuroraMysql version (#29888)

### Reason for this change

[Aurora MySQL database engine updates 2024-03-26 (version 2.11.5, compatible with MySQL 5.7.12)](https://docs.aws.amazon.com/AmazonRDS/latest/AuroraMySQLReleaseNotes/AuroraMySQL.Updates.2115.html)

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

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

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

@@ -537,6 +537,8 @@ export class AuroraMysqlEngineVersion {
   public static readonly VER_2_11_3 = AuroraMysqlEngineVersion.builtIn_5_7('2.11.3');
   /** Version "5.7.mysql_aurora.2.11.4". */
   public static readonly VER_2_11_4 = AuroraMysqlEngineVersion.builtIn_5_7('2.11.4');
+  /** Version "5.7.mysql_aurora.2.11.5". */
+  public static readonly VER_2_11_5 = AuroraMysqlEngineVersion.builtIn_5_7('2.11.5');
   /** Version "5.7.mysql_aurora.2.12.0". */
   public static readonly VER_2_12_0 = AuroraMysqlEngineVersion.builtIn_5_7('2.12.0');
   /** Version "5.7.mysql_aurora.2.12.1". */