Update dependency slack-notifier to v2 (#3400)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Gemfile

@@ -37,7 +37,7 @@ gem 'mqtt'                        # MQTTAgent
 gem 'net-ftp'
 gem 'net-ftp-list'                # FtpsiteAgent
 gem 'rturk', '~> 2.12.1'          # HumanTaskAgent
-gem 'slack-notifier', '~> 1.5.1'  # SlackAgent
+gem 'slack-notifier', '~> 2.4.0'  # SlackAgent
 gem 'twilio-ruby', '~> 7.2.2'    # TwilioAgent
 gem 'xmpp4r', '~> 0.5.6'          # JabberAgent
 

Gemfile.lock

@@ -768,7 +768,7 @@ GEM
     simplecov-html (0.12.3)
     simplecov-lcov (0.8.0)
     simplecov_json_formatter (0.1.4)
-    slack-notifier (1.5.1)
+    slack-notifier (2.4.0)
     snaky_hash (2.0.1)
       hashie
       version_gem (~> 1.1, >= 1.1.1)
@@ -944,7 +944,7 @@ DEPENDENCIES
   shoulda-matchers
   simplecov
   simplecov-lcov (~> 0.8.0)
-  slack-notifier (~> 1.5.1)
+  slack-notifier (~> 2.4.0)
   spectrum-rails
   spring
   spring-commands-rspec