Remove unnecessary env var and cleanup

app/controllers/projects/environments_controller.rb

@@ -223,7 +223,7 @@ class Projects::EnvironmentsController < Projects::ApplicationController
   def metrics_dashboard_params
     params
       .permit(:embedded, :group, :title, :y_label, :dashboard_path, :environment, :sample_metrics)
-      .merge(dashboard_path: params[:dashboard], environment: environment, sample_metrics: params[:sample_metrics])
+      .merge(dashboard_path: params[:dashboard], environment: environment)
   end
 
   def include_all_dashboards?

spec/controllers/projects/environments/sample_metrics_controller_spec.rb

@@ -9,17 +9,6 @@ describe Projects::Environments::SampleMetricsController do
   let_it_be(:environment) { create(:environment, project: project) }
   let_it_be(:user) { create(:user) }
 
-  before(:context) do
-    RSpec::Mocks.with_temporary_scope do
-      stub_env('USE_SAMPLE_METRICS', 'true')
-      Rails.application.reload_routes!
-    end
-  end
-
-  after(:context) do
-    Rails.application.reload_routes!
-  end
-
   before do
     project.add_reporter(user)
     sign_in(user)

spec/lib/gitlab/metrics/dashboard/processor_spec.rb

@@ -87,7 +87,7 @@ describe Gitlab::Metrics::Dashboard::Processor do
         end
       end
 
-      context 'when sample metrics are present' do
+      context 'when sample_metrics are requested' do
         let(:process_params) { [project, dashboard_yml, sequence, { environment: environment, sample_metrics: true }] }
 
         it 'includes a sample metrics path for the prometheus endpoint with each metric' do