Implement empty postRun() for Gerrit 2.9-SNAPSHOT

Current Gerrit master requires the plugins InitStep
to implement a postRun() action: we do not have anything
to execute so we leave the method empty.

Change-Id: Ib5247f339fd97c259f85f16eef9c1c114345d91a

github-plugin/src/main/java/com/googlesource/gerrit/plugins/github/InitGitHub.java

diff --git a/github-plugin/src/main/java/com/googlesource/gerrit/plugins/github/InitGitHub.java b/github-plugin/src/main/java/com/googlesource/gerrit/plugins/github/InitGitHub.java
index ffc7da5..5e56cf9 100644
--- a/github-plugin/src/main/java/com/googlesource/gerrit/plugins/github/InitGitHub.java
+++ b/github-plugin/src/main/java/com/googlesource/gerrit/plugins/github/InitGitHub.java
@@ -52,4 +52,8 @@
     auth.set("type", "HTTP");
     httpd.set("filterClass", "com.googlesource.gerrit.plugins.github.oauth.OAuthFilter");
   }
+
+  @Override
+  public void postRun() throws Exception {
+  }
 }