Maven: Build with 2.15.8 API

Change-Id: I0ac89efe3110b375be0d545a3db3342d4276b8f9
diff --git a/pom.xml b/pom.xml
index 8c48fa5..9e9f705 100644
--- a/pom.xml
+++ b/pom.xml
@@ -25,7 +25,7 @@
     <groupId>com.cisco.gerrit.plugins</groupId>
     <artifactId>slack-integration</artifactId>
     <packaging>jar</packaging>
-    <version>2.15.6</version>
+    <version>2.15.8</version>
     <name>Slack Integration Plugin</name>
 
     <properties>