Replace @npm_bazel_rollup with @npm//@bazel/rollup

This is needed after we have rules_nodejs upgraded to 2.0

Change-Id: I1fb3e41d93892bb7a9b6ea9884d582f7d809c446

gr-checks/BUILD

diff --git a/gr-checks/BUILD b/gr-checks/BUILD
index 0f931db..034acd2 100644
--- a/gr-checks/BUILD
+++ b/gr-checks/BUILD
@@ -1,4 +1,4 @@
-load("@npm_bazel_rollup//:index.bzl", "rollup_bundle")
+load("@npm//@bazel/rollup:index.bzl", "rollup_bundle")
 load("//tools/bzl:js.bzl", "polygerrit_plugin")
 load("//tools/bzl:genrule2.bzl", "genrule2")