Update read-write DB configuration after LPS-78134 changes

• Type: Task
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 7.0.x
• Component/s: Performance & Fault Tolerance
• Labels: None
• Git Pull Request: https://github.com/sez11a/liferay-docs/pull/2892

Documentation of both:

• https://dev.liferay.com/discover/deployment/-/knowledge_base/7-0/liferay-clustering#read-writer-database-configuration
• https://customer.liferay.com/documentation/7.0/deploy/-/official_documentation/deployment/liferay-clustering

Is out of date after LPS-78134 changes.