Update 'Supported Platforms' documentation

Issue Summary

The document Supported Platforms for pretty much all Jira versions states the following in regards to Oracle databases:

• JDBC Driver: For all Oracle versions, use the JDBC 19.3 (ojdbc8) driver listed here. This is the driver we’re using to test Jira with Oracle.

However, the Oracle JDBC 19.3 driver is no longer available on the linked page. It is still available at this link, instead: https://mvnrepository.com/artifact/com.oracle.ojdbc/ojdbc8/19.3.0.0

This is reproducible on Data Center: yes

Steps to Reproduce

Navigate to the Supported Platforms document.

Expected Results

It is possible to download the Oracle JDBC 19.3 driver from the page linked in our documentation.

Actual Results

The linked page no longer lists version 19.3 of the driver.

Workaround

Download Oracle JDBC 19.3 driver from this page instead:

• https://mvnrepository.com/artifact/com.oracle.ojdbc/ojdbc8/19.3.0.0