Improve dependency on com.google.errorprone:javac

https://checkerframework.org/manual/#maven does not explain what the com.google.errorprone:javac dependency is needed for.

If it is a Java compiler, it seems odd to be a runtime dependency.
If it is a dependency of the Checker Framework itself, which runs as an annotation processor, it should be a dependency in the section. Even better, org.checkerframework:checker (as supplied in should itself declare its dependency on javac.

Another, minor point: The section declares true. It shouldn't do that, it's the responsibility of the respective release engineer to decide whether forking is a good idea or not - unless Checker Framework explicitly requires a fork, in which case the configuration snippet should explain why.

Start with the Maven section at https://checkerframework.org/manual/#maven and inspect how com.google.errorprone:javac, annotationProcessorPaths, and the fork setting are presented. Confirm the dependency and fork requirements, then update the documentation so their purpose, placement, and any required behavior are explicit.