Describe the bug

Wrong link destination.

To Reproduce

Steps to reproduce the behavior:

1. Go to the Query Workbench
2. Select 'PPL' as the query language.
3. Click 'PPL Documentation'
4. Arrive at https://opensearch.org/docs/latest/

Expected behavior
Clicking 'PPL Documentation' should lead to https://opensearch.org/docs/latest/observability/ppl/index/

OpenSearch Version
1.2.0

Dashboards Version
1.2.0

opensearch-project/OpenSearch-Dashboards#592