Update Gerrit API version to 2.9

9f4de526dd3fec0400f6df53628956a4bf0d9033 removed TrackingIds table.
Remove the code that cleans this table during project deletion too.

Change-Id: I1a0cd70adda28f19d28c76fc9bc67bac2c6180e5
diff --git a/pom.xml b/pom.xml
index bc24942..7bd5f17 100644
--- a/pom.xml
+++ b/pom.xml
@@ -22,7 +22,7 @@
   <groupId>com.googlesource.gerrit.plugins</groupId>
   <artifactId>delete-project</artifactId>
   <packaging>jar</packaging>
-  <version>2.8-SNAPSHOT</version>
+  <version>2.9-SNAPSHOT</version>
   <properties>
     <Gerrit-ApiType>plugin</Gerrit-ApiType>
     <Gerrit-ApiVersion>${project.version}</Gerrit-ApiVersion>
diff --git a/src/main/java/com/googlesource/gerrit/plugins/deleteproject/database/Schema73DatabaseDeleteHandler.java b/src/main/java/com/googlesource/gerrit/plugins/deleteproject/database/Schema73DatabaseDeleteHandler.java
index c4853b4..b0248cf 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/deleteproject/database/Schema73DatabaseDeleteHandler.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/deleteproject/database/Schema73DatabaseDeleteHandler.java
@@ -121,7 +121,6 @@
       db.patchSetApprovals().delete(db.patchSetApprovals().byChange(id));
       db.changeMessages().delete(db.changeMessages().byChange(id));
       db.starredChanges().delete(db.starredChanges().byChange(id));
-      db.trackingIds().delete(db.trackingIds().byChange(id));
       db.changes().delete(Collections.singleton(change));
     }
   }