Merge branch 'revert-file-update-checker' into 'master'

Revert to non-evented file watcher

See merge request gitlab-org/gitlab!24167

Gemfile

@@ -332,7 +332,6 @@ group :metrics do
 end
 
 group :development do
-  gem 'listen', '~> 3.0'
   gem 'brakeman', '~> 4.2', require: false
   gem 'danger', '~> 6.0', require: false
 

Gemfile.lock

@@ -1279,7 +1279,6 @@ DEPENDENCIES
   license_finder (~> 5.4)
   licensee (~> 8.9)
   liquid (~> 4.0)
-  listen (~> 3.0)
   lograge (~> 0.5)
   loofah (~> 2.2)
   lru_redux

config/environments/development.rb

@@ -50,8 +50,4 @@ Rails.application.configure do
 
   # BetterErrors live shell (REPL) on every stack frame
   BetterErrors::Middleware.allow_ip!("127.0.0.1/0")
-
-  # Use an evented file watcher to asynchronously detect changes in source code,
-  # routes, locales, etc. This feature depends on the listen gem.
-  config.file_watcher = ActiveSupport::EventedFileUpdateChecker
 end