Fix UnusedVariable bug pattern flagged by error prone

Details: https://errorprone.info/bugpattern/UnusedVariable
Change-Id: I3f91cd9e3e61918539011c63fc0c2f63a43f2e93

src/test/java/com/googlesource/gerrit/plugins/webhooks/PostTaskTest.java

diff --git a/src/test/java/com/googlesource/gerrit/plugins/webhooks/PostTaskTest.java b/src/test/java/com/googlesource/gerrit/plugins/webhooks/PostTaskTest.java
index a2aed68..54aac2f 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/webhooks/PostTaskTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/webhooks/PostTaskTest.java
@@ -48,8 +48,6 @@
 
   @Mock private RemoteConfig remote;
 
-  @Mock private Configuration cfg;
-
   @Mock private HttpSession session;
 
   @Mock private HttpSession.Factory sessionFactory;