MM-53962: Adding ES8 dependency (#24399)

* Adding ES8 dependency

```release-note
NONE
```


Co-authored-by: Mattermost Build <build@mattermost.com>

e2e-tests/.ci/server.generate.sh

@@ -128,7 +128,7 @@ $(if mme2e_is_token_in_list "elasticsearch" "$ENABLED_DOCKER_SERVICES"; then
     if [ "$MME2E_ARCHTYPE" = "arm64" ]; then
       echo '
   elasticsearch:
-    image: mattermostdevelopment/mattermost-elasticsearch:7.17.10
+    image: mattermostdevelopment/mattermost-elasticsearch:8.9.0
     platform: linux/arm64/v8
     restart: "no"
     network_mode: host

e2e-tests/playwright/support/server/default_config.ts

@@ -589,6 +589,7 @@ const defaultServerConfig: AdminConfig = {
         ConnectionURL: 'http://localhost:9200',
         Username: 'elastic',
         Password: 'changeme',
+        Backend: 'elasticsearch',
         EnableIndexing: false,
         EnableSearching: false,
         EnableAutocomplete: false,