adding version 9.1.6 to the docs (elastic#3604)

this pr adds the version `9.1.6` to the list of ECE stackpacks

ref: elastic/cloud#148319

Author: nadirhamza1

deploy-manage/deploy/cloud-enterprise/ece-install-offline-images.md

@@ -72,6 +72,11 @@ Enterprise Search is not available in versions 9.0+.
 | docker.elastic.co/cloud-release/kibana-cloud:9.2.0 | ECE 4.0.0 |
 | docker.elastic.co/cloud-release/elastic-agent-cloud:9.2.0 | ECE 4.0.0 |
 |  |  |
+| [{{es}}, {{kib}}, APM, and Enterprise Search stack pack: 9.1.6](https://download.elastic.co/cloud-enterprise/versions/9.1.6.zip) | ECE 4.0.0 |
+| docker.elastic.co/cloud-release/elasticsearch-cloud-ess:9.1.6 | ECE 4.0.0 |
+| docker.elastic.co/cloud-release/kibana-cloud:9.1.6 | ECE 4.0.0 |
+| docker.elastic.co/cloud-release/elastic-agent-cloud:9.1.6 | ECE 4.0.0 |
+|  |  |
 | [{{es}}, {{kib}}, APM, and Enterprise Search stack pack: 9.1.5](https://download.elastic.co/cloud-enterprise/versions/9.1.5.zip) | ECE 4.0.0 |
 | docker.elastic.co/cloud-release/elasticsearch-cloud-ess:9.1.5 | ECE 4.0.0 |
 | docker.elastic.co/cloud-release/kibana-cloud:9.1.5 | ECE 4.0.0 |

deploy-manage/deploy/cloud-enterprise/manage-elastic-stack-versions.md

@@ -49,6 +49,7 @@ Following is the full list of available packs containing {{stack}} versions. Not
 | Stack pack download link | Minimum required ECE version |
 | --- | --- |
 | [{{es}}, {{kib}}, and APM stack pack: 9.2.0](https://download.elastic.co/cloud-enterprise/versions/9.2.0.zip) | ECE 4.0.0 |
+| [{{es}}, {{kib}}, and APM stack pack: 9.1.6](https://download.elastic.co/cloud-enterprise/versions/9.1.6.zip) | ECE 4.0.0 |
 | [{{es}}, {{kib}}, and APM stack pack: 9.1.5](https://download.elastic.co/cloud-enterprise/versions/9.1.5.zip) | ECE 4.0.0 |
 | [{{es}}, {{kib}}, and APM stack pack: 9.1.4](https://download.elastic.co/cloud-enterprise/versions/9.1.4.zip) | ECE 4.0.0 |
 | [{{es}}, {{kib}}, and APM stack pack: 9.1.3](https://download.elastic.co/cloud-enterprise/versions/9.1.3.zip) | ECE 4.0.0 |