Adapt to latest bazel release also in gerrit plugin rule

Changes I6a7a95001 and I7ce041f7d adapted rules to bazel's deprecation
of the set() method, but missed the gerrit plugin rule.

Change-Id: Iddd8a973587df761bab3aa61db1a2ef87c70c603
diff --git a/gerrit_plugin.bzl b/gerrit_plugin.bzl
index 04fb20b..c75a5ab 100644
--- a/gerrit_plugin.bzl
+++ b/gerrit_plugin.bzl
@@ -58,7 +58,7 @@
   if gwt_module:
     native.java_library(
       name = name + '__gwt_module',
-      resources = list(set(srcs + resources)),
+      resources = list(depset(srcs + resources)),
       runtime_deps = deps + GWT_PLUGIN_DEPS,
       visibility = ['//visibility:public'],
     )