Improve version number documentation

Author: dr-jts

modules/core/src/main/java/org/locationtech/jts/JTSVersion.java

@@ -44,7 +44,9 @@ public class JTSVersion {
   public static final int PATCH = 1;
 
   /**
-   * An optional string providing further release info (such as "alpha 1");
+   * An optional string providing further release info.
+   * For snapshot releases this is "SNAPSHOT".
+   * For final releases it is the empty string.
    */
   private static final String RELEASE_INFO = "SNAPSHOT";