Fix javadoc warning

Change-Id: I4663f7620b5e04cb5e137c7fe977d2f3d1a8dfe0

src/main/java/com/googlesource/gerrit/plugins/forcedraft/ForceDraft.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/forcedraft/ForceDraft.java b/src/main/java/com/googlesource/gerrit/plugins/forcedraft/ForceDraft.java
index 7840751..88ac0d4 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/forcedraft/ForceDraft.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/forcedraft/ForceDraft.java
@@ -184,7 +184,7 @@
   /**
    * Updates parentChange to draft if every Patch set in Change is Draft.
    *
-   * @return
+   * @return the updated change
    * @throws OrmException
    */
   private Change updateChange() throws OrmException {