chore(opensearchservice): deprecate OpenSearch 2.10 (aws#29469)

### Issue # (if applicable)

None

### Reason for this change

Just a single diff between the SDK and the CDK this time, OpenSearch
v2.10 was removed, unsure why

### Description of changes

Marked `OPENSEARCH_2_10` as `@deprecated`

### Description of how you validated changes

It is neither listed in the
[docs](https://docs.aws.amazon.com/opensearch-service/latest/developerguide/supported-operations.html),
nor in the SDK/CLI output of `opensearch:ListVersions`:
```sh
$ aws opensearch list-versions | jq '.Versions[] | select(.=="OpenSearch_2.10")'
```

### 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*

Co-authored-by: GZ <yuanhaoz@amazon.com>

packages/aws-cdk-lib/aws-opensearchservice/lib/version.ts

@@ -90,7 +90,10 @@ export class EngineVersion {
   /** AWS OpenSearch 2.9 */
   public static readonly OPENSEARCH_2_9 = EngineVersion.openSearch('2.9');
 
-  /** AWS OpenSearch 2.10 */
+  /**
+   * AWS OpenSearch 2.10
+   * @deprecated use latest version of the OpenSearch engine
+   **/
   public static readonly OPENSEARCH_2_10 = EngineVersion.openSearch('2.10');
 
   /** AWS OpenSearch 2.11 */