bug 59804: javadoc update

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1751574 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/poi/util/Removal.java

@@ -51,6 +51,9 @@ public @interface Removal {
     /**
      * The POI version when this feature may be removed.
      * 
+     * To ensure that the version number can be compared to the current version
+     * and a unit test can generate a warning if a removal-eligible feature has
+     * not been removed yet, the version number should adhere to the following format:
      * Format: "(?<major>\d+)\.(?<minor>\d+)"
      * Example: "3.15"
      */