Remove unused constant GERRIT_ADMIN_PROTOCOL_PREFIX

The constant GERRIT_ADMIN_PROTOCOL_PREFIX was pulled in from
the replication plugin but isn't used in the pull-replication
plugin domain.

Change-Id: I8c9a646936d4f602462211ab9fc732925c021252

src/main/java/com/googlesource/gerrit/plugins/replication/pull/client/FetchRestApiClient.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/replication/pull/client/FetchRestApiClient.java b/src/main/java/com/googlesource/gerrit/plugins/replication/pull/client/FetchRestApiClient.java
index efc445d..c3bb378 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/replication/pull/client/FetchRestApiClient.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/replication/pull/client/FetchRestApiClient.java
@@ -70,7 +70,6 @@
   public static final boolean FORCE_ASYNC = true;
 
   private static final FluentLogger logger = FluentLogger.forEnclosingClass();
-  static String GERRIT_ADMIN_PROTOCOL_PREFIX = "gerrit+";
 
   private static final Gson GSON =
       new GsonBuilder().setFieldNamingPolicy(LOWER_CASE_WITH_UNDERSCORES).create();