Update Bullet gem to 6.0.2

We are having a problem with the Bullet gem:

An error occurred while loading ./spec/requests/api/users_spec.rb.
Failure/Error: require File.expand_path('../config/environment',
__dir__)

Bundler::GemRequireError: There was an error while trying to load the
gem 'bullet'.  Gem Load Error is: Bullet does not support active_record
ActiveRecord::VERSION yet

This update also adds support for Rails 5.2 and Rails 6.0

See the changelog:
https://github.com/flyerhzm/bullet/blob/master/CHANGELOG.md

The complete changes between versions:
https://github.com/flyerhzm/bullet/compare/5.5.0..6.0.2

Gemfile

@@ -346,7 +346,7 @@ group :development do
 end
 
 group :development, :test do
-  gem 'bullet', '~> 5.5.0', require: !!ENV['ENABLE_BULLET']
+  gem 'bullet', '~> 6.0.2', require: !!ENV['ENABLE_BULLET']
   gem 'pry-byebug', '~> 3.5.1', platform: :mri
   gem 'pry-rails', '~> 0.3.4'
 

Gemfile.lock

@@ -118,9 +118,9 @@ GEM
     brakeman (4.2.1)
     browser (2.5.3)
     builder (3.2.3)
-    bullet (5.5.1)
+    bullet (6.0.2)
       activesupport (>= 3.0.0)
-      uniform_notifier (~> 1.10.0)
+      uniform_notifier (~> 1.11)
     bundler-audit (0.5.0)
       bundler (~> 1.2)
       thor (~> 0.18)
@@ -1057,7 +1057,7 @@ GEM
     unicorn-worker-killer (0.4.4)
       get_process_mem (~> 0)
       unicorn (>= 4, < 6)
-    uniform_notifier (1.10.0)
+    uniform_notifier (1.13.0)
     unleash (0.1.5)
       murmurhash3 (~> 0.1.6)
     unparser (0.4.5)
@@ -1139,7 +1139,7 @@ DEPENDENCIES
   bootstrap_form (~> 4.2.0)
   brakeman (~> 4.2)
   browser (~> 2.5)
-  bullet (~> 5.5.0)
+  bullet (~> 6.0.2)
   bundler-audit (~> 0.5.0)
   capybara (~> 3.22.0)
   capybara-screenshot (~> 1.0.22)