Use a transient field for seen in FindJavaVersion

[timtebeek]

Same as in sibling recipe AboutJavaVersion

rewrite-migrate-java/src/main/java/org/openrewrite/java/migrate/search/AboutJavaVersion.java

Lines 37 to 39 in 0fe2aba

	public class AboutJavaVersion extends Recipe {
	transient JavaVersionPerSourceSet javaVersionPerSourceSet = new JavaVersionPerSourceSet(this);
	transient Set<ProjectSourceSet> seenSourceSets = new HashSet<>();