bazlets: Stop using native.git_repository

The native.git_repository method doesn't work in the latest version
of bazel, and causes the build to fail with:

  type 'struct' has no method git_repository()

Change-Id: I1a52871be391e18d7d35ddeff51bf5a537cb9aa3
diff --git a/bazlets.bzl b/bazlets.bzl
index f97b72c..f089af4 100644
--- a/bazlets.bzl
+++ b/bazlets.bzl
@@ -1,10 +1,12 @@
+load("@bazel_tools//tools/build_defs/repo:git.bzl", "git_repository")
+
 NAME = "com_googlesource_gerrit_bazlets"
 
 def load_bazlets(
         commit,
         local_path = None):
     if not local_path:
-        native.git_repository(
+        git_repository(
             name = NAME,
             remote = "https://gerrit.googlesource.com/bazlets",
             commit = commit,