Fix JS compression error by running Ugilifier in harmony mode

When building the docker image in production with script/docker/update
we get a new error:

```
```

We follow the instruction to use `Uglifier.new(:harmony => true)` and
sure enought the error is silenced.

config/environments/production.rb

@@ -27,7 +27,7 @@
   config.public_file_server.enabled = ENV["RAILS_SERVE_STATIC_FILES"].present?
 
   # Compress JavaScripts and CSS.
-  config.assets.js_compressor = :uglifier
+  config.assets.js_compressor = Uglifier.new(harmony: true)
   # Set a css_compressor so sassc-rails does not overwrite the compressor when running the tests
   config.assets.css_compressor = nil