RebaseChange: Fix typo

Change-Id: I8f8fd169ce258191b2f1fcc70e0673edb7eadc9d
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/changedetail/RebaseChange.java b/gerrit-server/src/main/java/com/google/gerrit/server/changedetail/RebaseChange.java
index 8de6904..286d178 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/changedetail/RebaseChange.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/changedetail/RebaseChange.java
@@ -182,7 +182,7 @@
 
       if (patchSetAncestors.size() > 1) {
         throw new IOException(
-            "Cannot rebase a change with multiple parents. Parents commits: "
+            "Cannot rebase a change with multiple parents. Parent commits: "
                 + patchSetAncestors.toString());
       }
       if (patchSetAncestors.size() == 0) {