[Docs] Document request URI too long workaround for reporting

[bczifra]

Describe the feature:
Report generation can fail for large reports because the request URI is too long. The workaround is to break the report up into smaller pieces. It would be helpful to document this on https://www.elastic.co/guide/en/kibana/current/reporting-troubleshooting.html .

Describe a specific use case for the feature:
To allow users to easily determine a workaround when they encounter this error.

[elasticmachine]

Pinging @elastic/kibana-docs

[tsullivan]

Unfortunately tthere is no workaround that we can faithfully support. Therefore, we're treating this as a bug and expect to have a fix in the next minor version of Kibana.

Closing for #20037