Update Gerrit API version to 2.8 in pom.xml

Change-Id: Id855e7aea62409d9581c02eb16e2c293c6eafe57

pom.xml

diff --git a/pom.xml b/pom.xml
index 6db3f29..a6a84e6 100644
--- a/pom.xml
+++ b/pom.xml
@@ -23,7 +23,7 @@
   <name>commit-message-length-validator</name>
   <groupId>com.googlesource.gerrit.plugins.validators</groupId>
   <packaging>jar</packaging>
-  <version>2.8-SNAPSHOT</version>
+  <version>2.8</version>
 
   <properties>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>