latest.stable.released property is never used and out of date

The latest.stable.released property was introduced in the following commit: Improved download page generation. Added release id property by michele.mostarda in 2012 and later all of its usages were replaced by hardcoded constants in the following commit: Updates to all Website documentation to reflect 2.0 release by lewismc in 2017.

We should either delete this property or update it (as it currently indicates version 2.1) and add it back into the src/site/xdoc/download.xml.vm file.

Lewis, do you have any insight on this?