[errorprone] Remove unused PostTaskTest#cfg

See https://errorprone.info/bugpattern/UnusedVariable

Release-Notes: skip
Change-Id: I2a7c788bbc8386c53d662672d56064fb0bda5e42
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;