Use rules_pkg in the java-export example (#1628)

The example loaded `pkg_tar` from `@bazel_tools//tools/build_defs/pkg:pkg.bzl`, which has been deprecated in favor of rules_pkg for years and is slated for removal from `@bazel_tools`.

examples/java-export/MODULE.bazel

diff --git a/examples/java-export/MODULE.bazel b/examples/java-export/MODULE.bazel
index 951674f..289c879 100644
--- a/examples/java-export/MODULE.bazel
+++ b/examples/java-export/MODULE.bazel
@@ -5,6 +5,7 @@
 bazel_dep(name = "protobuf", version = protobuf_version)
 bazel_dep(name = "rules_java", version = "9.3.0")
 bazel_dep(name = "rules_jvm_external", version = "ignored")
+bazel_dep(name = "rules_pkg", version = "1.3.0")
 bazel_dep(name = "rules_proto", version = "7.1.0")
 
 local_path_override(

examples/java-export/src/main/java/com/github/bazelbuild/rulesjvmexternal/example/export/BUILD

diff --git a/examples/java-export/src/main/java/com/github/bazelbuild/rulesjvmexternal/example/export/BUILD b/examples/java-export/src/main/java/com/github/bazelbuild/rulesjvmexternal/example/export/BUILD
index 09af32d..f917379 100644
--- a/examples/java-export/src/main/java/com/github/bazelbuild/rulesjvmexternal/example/export/BUILD
+++ b/examples/java-export/src/main/java/com/github/bazelbuild/rulesjvmexternal/example/export/BUILD
@@ -1,6 +1,6 @@
-load("@bazel_tools//tools/build_defs/pkg:pkg.bzl", "pkg_tar")
 load("@rules_java//java:java_library.bzl", "java_library")
 load("@rules_jvm_external//:defs.bzl", "artifact")
+load("@rules_pkg//pkg:tar.bzl", "pkg_tar")
 
 java_library(
     name = "export",