MM-53962: Adding ES8 dependency (#24399)

* Adding ES8 dependency

```release-note
NONE
```


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

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,