Remove unique validation from external_url in Environment

app/models/environment.rb

@@ -30,7 +30,6 @@ class Environment < ActiveRecord::Base
                       message: Gitlab::Regex.environment_slug_regex_message }
 
   validates :external_url,
-            uniqueness: { scope: :project_id },
             length: { maximum: 255 },
             allow_nil: true,
             addressable_url: true

spec/models/environment_spec.rb

@@ -18,7 +18,6 @@ describe Environment do
   it { is_expected.to validate_length_of(:slug).is_at_most(24) }
 
   it { is_expected.to validate_length_of(:external_url).is_at_most(255) }
-  it { is_expected.to validate_uniqueness_of(:external_url).scoped_to(:project_id) }
 
   describe '.order_by_last_deployed_at' do
     let(:project) { create(:project, :repository) }