Explictly require hangouts-chat in Gemfile

After the model `HangoutsChatService` was renamed
`Integrations::HangoutsChat`, the `require "hangouts_chat"` in
`config/initializers/hangouts_chat_http_override.rb` would load the
model and not the gem. This would cause the initializer to define a
new `HangoutsChat::Sender::HTTP` class rather than redefine an existing
class.

!61957
#201855

Gemfile

@@ -253,7 +253,7 @@ gem 'flowdock', '~> 0.7'
 gem 'slack-messenger', '~> 2.3.4'
 
 # Hangouts Chat integration
-gem 'hangouts-chat', '~> 0.0.5'
+gem 'hangouts-chat', '~> 0.0.5', require: 'hangouts_chat'
 
 # Asana integration
 gem 'asana', '~> 0.10.3'

app/models/integrations/chat_notification.rb

@@ -91,7 +91,6 @@ def default_fields
     end
 
     def execute(data)
-      # binding.pry
       return unless supported_events.include?(data[:object_kind])
 
       return unless notify_label?(data)

app/models/integrations/hangouts_chat.rb

 # frozen_string_literal: true
 
-require 'hangouts_chat'
-
 module Integrations
   class HangoutsChat < ChatNotification
     include ActionView::Helpers::UrlHelper

spec/support/shared_examples/models/chat_integration_shared_examples.rb

@@ -53,7 +53,6 @@
       end
 
       it "calls #{integration_name} API" do
-        # binding.pry
         result = subject.execute(sample_data)
 
         expect(result).to be(true)