chore(rds): add MariaDB versions 10.6.23, 10.11.14, and 11.4.8

[Tietew]

Reason for this change

New MariaDB versions are available.
https://aws.amazon.com/about-aws/whats-new/2025/08/amazon-rds-mariadb-community-minor-versions/

Some MariaDB versions are removed from available engine versions.

Description of changes

• Added MariaDB versions: 10.6.23, 10.11.14, and 11.4.8
• Marked as deprecated MariaDB versions: 10.5.20-24, 10.6.13-17, 10.11.4-7

Describe any new or updated permissions being added

N/A

Description of how you validated changes

$ aws --region us-east-1 rds describe-db-engine-versions --engine 'mariadb' --query 'DBEngineVersions[].EngineVersion' --output table
--------------------------
|DescribeDBEngineVersions|
+------------------------+
|  10.5.25               |
|  10.5.26               |
|  10.5.27               |
|  10.5.28               |
|  10.5.29               |
|  10.6.18               |
|  10.6.19               |
|  10.6.20               |
|  10.6.21               |
|  10.6.22               |
|  10.6.23               |
|  10.11.8               |
|  10.11.9               |
|  10.11.10              |
|  10.11.11              |
|  10.11.13              |
|  10.11.14              |
|  11.4.3                |
|  11.4.4                |
|  11.4.5                |
|  11.4.7                |
|  11.4.8                |
|  11.8.3                |
+------------------------+

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

---

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