Fix link to Eland docs (elastic#172879)

elastic#171024 introduced the following
link to the doc link service:

```
eland: `${ELASTIC_WEBSITE_URL}guide/en/elasticsearch/client/eland/${DOC_LINK_VERSION}/index.html`
```

However, it looks like the Eland client docs are not versioned, but
always on `current`. This PR fixes the link.

packages/kbn-doc-links/src/get_doc_links.ts

@@ -822,7 +822,7 @@ export const getDocLinks = ({ kibanaBranch }: GetDocLinkOptions): DocLinks => {
       rubyOverview: `${ELASTIC_WEBSITE_URL}guide/en/elasticsearch/client/ruby-api/${DOC_LINK_VERSION}/ruby_client.html`,
       rustGuide: `${ELASTIC_WEBSITE_URL}guide/en/elasticsearch/client/rust-api/${DOC_LINK_VERSION}/index.html`,
       rustOverview: `${ELASTIC_WEBSITE_URL}guide/en/elasticsearch/client/rust-api/${DOC_LINK_VERSION}/overview.html`,
-      eland: `${ELASTIC_WEBSITE_URL}guide/en/elasticsearch/client/eland/${DOC_LINK_VERSION}/index.html`,
+      eland: `${ELASTIC_WEBSITE_URL}guide/en/elasticsearch/client/eland/current/index.html`,
     },
     endpoints: {
       troubleshooting: `${SECURITY_SOLUTION_DOCS}ts-management.html#ts-endpoints`,