Sample plugin requires Java 17

[ppazos]

Because of this dependency [ERROR] Failed to execute goal org.bsc.maven:maven-processor-plugin:5.1:process (process) on project shared: Error executing: error: invalid source release: 17 -> [Help 1]

Though the README mentions to use Java 8. Might need a bump?

[jonbartels]

#4 shows the same error. I know we fixed it but I don't see which PR or commit solved the problem.