gerrit_polymer: Update rules_nodejs to match Gerrit 3.5.2+

This updates to 5.1.0 which does have breaking changes for users. See
[1] and [2] for background info on the rules_nodejs release.

Users of gerrit_polymer should update .bazelversion to at least 5.0.0
and update WORKSPACE files similar to how Gerrit core was updated in
Change Iba20c21e9a6.

[1] https://github.com/bazelbuild/rules_nodejs/releases/tag/5.0.0
[2] https://github.com/bazelbuild/rules_nodejs/wiki/Migrating-to-5.0

Change-Id: I5170d3d20c7c41a49b62c9f7501d1e209eef7f6a
diff --git a/gerrit_polymer.bzl b/gerrit_polymer.bzl
index 735d22f..bb448de 100644
--- a/gerrit_polymer.bzl
+++ b/gerrit_polymer.bzl
@@ -19,6 +19,6 @@
 
     http_archive(
         name = "build_bazel_rules_nodejs",
-        sha256 = "1134ec9b7baee008f1d54f0483049a97e53a57cd3913ec9d6db625549c98395a",
-        urls = ["https://github.com/bazelbuild/rules_nodejs/releases/download/3.4.0/rules_nodejs-3.4.0.tar.gz"],
+        sha256 = "c077680a307eb88f3e62b0b662c2e9c6315319385bc8c637a861ffdbed8ca247",
+        urls = ["https://github.com/bazelbuild/rules_nodejs/releases/download/5.1.0/rules_nodejs-5.1.0.tar.gz"],
     )