Add Java 11+ requirement to README (#6272)
Add Java 11+ requirement to README (#6272)

## What is the goal of this PR?

We added the requirement of running Java 11+ to the README file.

## What are the changes implemented in this PR?

Add Java 11+ requirement to README

graknlabs/grakn,graknlabs/grakn,graknlabs/grakn,graknlabs/grakn