Use genrule2 rule implementation from bazlets

Change-Id: Ib0109736b7ad729ea64443ecbc3274c021937c9a

BUILD

diff --git a/BUILD b/BUILD
index fc5be7e..dd927af 100644
--- a/BUILD
+++ b/BUILD
@@ -1,4 +1,4 @@
-load("//tools/bzl:genrule2.bzl", "genrule2")
+load("@com_googlesource_gerrit_bazlets//tools:genrule2.bzl", "genrule2")
 load("@com_googlesource_gerrit_bazlets//:gerrit_plugin.bzl", "gerrit_plugin", "gerrit_plugin_tests")
 
 gerrit_plugin(