Add instruction to uncheck Cacheable checkbox

We had gotten a complaint about our Nosester Velocity template not working correctly for 6.1 (comment from reader). The only way the template works is if the *Cacheable* checkbox is unchecked. This was added to the instructions to avoid confusion. Also included some minor formatting.

https://issues.liferay.com/browse/LRDOCS-716
https://issues.liferay.com/browse/LRDOCS-771 (also sending fix for 6.2)