chore(rds): support 11.4.3 engine version for MariaDB (#31769)

Add new engine version

Ref: https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/MariaDB.Concepts.VersionMgmt.html#MariaDB.Concepts.VersionMgmt.Supported

```sh
% aws rds describe-db-engine-versions --engine mariadb --query "DBEngineVersions[?EngineVersion=='11.4.3'].[DBEngineVersionDescription,EngineVersion,DBParameterGroupFamily,MajorEngineVersion,Status]" --output json
[
    [
        "MariaDB 11.4.3",
        "11.4.3",
        "mariadb11.4",
        "11.4",
        "available"
    ]
]
```


### 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)

----

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

Author: mazyu36

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

@@ -558,6 +558,8 @@ export class MariaDbEngineVersion {
   public static readonly VER_10_11_8 = MariaDbEngineVersion.of('10.11.8', '10.11');
   /** Version "10.11.9". */
   public static readonly VER_10_11_9 = MariaDbEngineVersion.of('10.11.9', '10.11');
+  /** Version "11.4.3". */
+  public static readonly VER_11_4_3 = MariaDbEngineVersion.of('11.4.3', '11.4');
 
   /**
    * Create a new MariaDbEngineVersion with an arbitrary version.

packages/aws-cdk-lib/aws-rds/test/instance-engine.test.ts

@@ -296,6 +296,7 @@ describe('instance engine', () => {
       ['10.11.7', rds.MariaDbEngineVersion.VER_10_11_7],
       ['10.11.8', rds.MariaDbEngineVersion.VER_10_11_8],
       ['10.11.9', rds.MariaDbEngineVersion.VER_10_11_9],
+      ['11.4.3', rds.MariaDbEngineVersion.VER_11_4_3],
     ])('is passed correctly for %s', (engineVersion, version) => {
 
       // WHEN