README.md References to OpenRocket Need Updating

[DrRocketry]

The next release of OpenRocket is just around the corner, using JDK 11.0.13, and it appears to compile using JDK 17.0.1, having no new errors.

          "Note, OpenRocket only works on Java 8 and below. Check out the readme in rocket_farm."

JP Johnston ME CSWP