Use correct `Environment`-class within `Gitlab` namespace

lib/gitlab/prometheus/queries/additional_metrics_environment_query.rb

@@ -5,7 +5,7 @@ module Gitlab
         include QueryAdditionalMetrics
         def query(environment_id)
-          Environment.find_by(id: environment_id).try do |environment|
+          ::Environment.find_by(id: environment_id).try do |environment|
             query_metrics(
               common_query_context(environment, timeframe_start: 8.hours.ago.to_f, timeframe_end: Time.now.to_f)
             )

lib/gitlab/prometheus/queries/environment_query.rb

@@ -3,7 +3,7 @@ module Gitlab
     module Queries
       class EnvironmentQuery < BaseQuery
         def query(environment_id)
-          Environment.find_by(id: environment_id).try do |environment|
+          ::Environment.find_by(id: environment_id).try do |environment|
             environment_slug = environment.slug
             timeframe_start = 8.hours.ago.to_f
             timeframe_end = Time.now.to_f

lib/gitlab/usage_data.rb

@@ -27,8 +27,8 @@ module Gitlab
             ci_pipeline_schedules: ::Ci::PipelineSchedule.count,
             deploy_keys: DeployKey.count,
             deployments: Deployment.count,
-            environments: Environment.count,
-            in_review_folder: Environment.in_review_folder.count,
+            environments: ::Environment.count,
+            in_review_folder: ::Environment.in_review_folder.count,
             groups: Group.count,
             issues: Issue.count,
             keys: Key.count,