Include SnowplowHelpers only when :snowplow metadata was provided

spec/spec_helper.rb

@@ -130,7 +130,6 @@ RSpec.configure do |config|
   config.include StubExperiments
   config.include StubGitlabCalls
   config.include StubGitlabData
-  config.include SnowplowHelpers
   config.include NextFoundInstanceOf
   config.include NextInstanceOf
   config.include TestEnv

spec/support/snowplow.rb

 # frozen_string_literal: true
 
 RSpec.configure do |config|
+  config.include SnowplowHelpers, :snowplow
+
   config.before(:each, :snowplow) do
     # Using a high buffer size to not cause early flushes
     buffer_size = 100