Remove no more used variable "static_jars"

The variable is no more used in gerrit_plugin.bzl since 60bb597a9b
removed support for GWT plugins in November 2018.

Change-Id: Idc180710f0a66413b5cd4fa6f97c759353694bd2

gerrit_plugin.bzl

diff --git a/gerrit_plugin.bzl b/gerrit_plugin.bzl
index 4021733..44bffc5 100644
--- a/gerrit_plugin.bzl
+++ b/gerrit_plugin.bzl
@@ -25,8 +25,6 @@
         dir_name = None,
         target_suffix = "",
         **kwargs):
-    static_jars = []
-
     if not dir_name:
         dir_name = name
 
@@ -42,9 +40,7 @@
         name = "%s__non_stamped" % name,
         deploy_manifest_lines = manifest_entries + ["Gerrit-ApiType: plugin"],
         main_class = "Dummy",
-        runtime_deps = [
-            ":%s__plugin" % name,
-        ] + static_jars,
+        runtime_deps = [":%s__plugin" % name],
         visibility = ["//visibility:public"],
     )