convert rules using pkg_tar in //third_party to rules_pkg

Partial commit for third_party/*, see #8932.

Signed-off-by: iirina <elenairina@google.com>
diff --git a/third_party/BUILD b/third_party/BUILD
index 75b0b60..eec39b3 100644
--- a/third_party/BUILD
+++ b/third_party/BUILD
@@ -1,6 +1,6 @@
 package(default_visibility = ["//visibility:public"])
 
-load("//tools/build_defs/pkg:pkg.bzl", "pkg_tar")
+load("@rules_pkg//:pkg.bzl", "pkg_tar")
 
 filegroup(
     name = "srcs",
diff --git a/third_party/ijar/BUILD b/third_party/ijar/BUILD
index 466c7d4..8f78c9c 100644
--- a/third_party/ijar/BUILD
+++ b/third_party/ijar/BUILD
@@ -7,7 +7,7 @@
 
 licenses(["notice"])  # Apache 2.0
 
-load("//tools/build_defs/pkg:pkg.bzl", "pkg_tar")
+load("@rules_pkg//:pkg.bzl", "pkg_tar")
 
 cc_library(
     name = "zip",