Fix list of privileges in Opensearch

[sdorokhova]

We have documented the list of user privileges required to run Camunda 8 with Opensearch.

But it looks like, either the docs are not full, or the list of privileges is different for different Opensearch versions.

Related support case: https://jira.camunda.com/browse/SUPPORT-23578
The customer has to add the following privileges additionally to those documented:

cluster:admin/component_template/put
indices:data/write/bulk
indices:data/read/scroll