Fixes RepositoryValidationService spec

Add 'Rspec' at the beginning of the spec

spec/services/snippets/repository_validation_service_spec.rb

@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-describe Snippets::RepositoryValidationService do
+RSpec.describe Snippets::RepositoryValidationService do
   describe '#execute' do
     let_it_be(:user)    { create(:user) }
     let_it_be(:snippet) { create(:personal_snippet, :empty_repo, author: user) }