Enable asset compression in production.

`config.assets.compress` needed to be explicitly enabled.

Follow-up to !3544. Resolves #14344.

CHANGELOG

 Please view this file on the master branch, on stable branches it's out of date.
 
 v 8.7.0 (unreleased)
+  - Enable gzip for assets, makes the page size significantly smaller. !3544 / !3632 (Connor Shea)
   - Load award emoji images separately unless opening the full picker. Saves several hundred KBs of data for most pages. (Connor Shea)
   - All images in discussions and wikis now link to their source files !3464 (Connor Shea).
   - Return status code 303 after a branch DELETE operation to avoid project deletion (Stan Hu)

config/environments/production.rb

@@ -21,6 +21,9 @@ Rails.application.configure do
   # Generate digests for assets URLs
   config.assets.digest = true
 
+  # Enable compression of compiled assets using gzip.
+  config.assets.compress = true
+
   # Defaults to nil and saved in location specified by config.assets.prefix
   # config.assets.manifest = YOUR_PATH