Please improve documentation related to Java 11 requirements

#### Is your feature request related to a problem? Please describe.**
> Upgrading the plugin to v2.0.2 causes analysis failures with SonarQube scanners older than version 4.0 because the plugin is compiled with Java 11 and the v3.x of the SonarQube Scanner has a v1.8 embedded JRE.

#### Describe the solution you'd like
> Update the documentation and release notes to indicate that a Java 11 JRE is required to use the plugin, not just that the plugin supports Java 11.

#### Describe alternatives you've considered
> _A clear and concise description of any alternative solutions or features you've considered._

#### Additional context
> _Add any other context or screenshots about the feature request here._

Review the plugin documentation and release notes for the current Java compatibility wording. Confirm that both explicitly state a Java 11 JRE is required, including for scanner usage; the issue is done when the requirement is no longer described only as Java 11 support.

Written by the indexing model from the issue text.