Fix path for rules_pkg providers.bzl load

We use PackageVariablesInfo from rules_pkg for versioning. The
previous change bumped the version of our rules_pkg dependency and it
looks like that moved the declaring providers.bzl file change to a
`pkg/` subdir.

This broke our Windows builds/release automation since they use
//:dist_zip. We did not catch this during PR testing because we just
do `npm test`.

Author: dibenede

protobuf_javascript_release.bzl

@@ -1,7 +1,7 @@
 """Generates package naming variables for use with rules_pkg."""
 
 load("@bazel_tools//tools/cpp:toolchain_utils.bzl", "find_cpp_toolchain")
-load("@rules_pkg//:providers.bzl", "PackageVariablesInfo")
+load("@rules_pkg//pkg:providers.bzl", "PackageVariablesInfo")
 
 _PROTOBUF_JAVASCRIPT_VERSION = "3.21.4"