use INNER JOIN instead of LEFT JOIN

as we're using UNION now we can use INNER JOIN.

app/models/ci/runner.rb

@@ -29,22 +29,13 @@ module Ci
     scope :ordered, ->() { order(id: :desc) }
 
     scope :owned_or_shared, ->(project_id) do
-      project_runners = joins(
-        %{
-          LEFT JOIN ci_runner_projects ON ci_runner_projects.runner_id = ci_runners.id
-        }
-      ).where(
-        %{
-          ci_runner_projects.project_id = :project_id
-        },
-        project_id: project_id
-      )
+      project_runners = joins(:runner_projects).where(ci_runner_projects: { project_id: project_id })
 
       group_runners = joins(
         %{
-          LEFT JOIN ci_runner_groups ON ci_runner_groups.runner_id = ci_runners.id
-          LEFT JOIN namespaces ON namespaces.id = ci_runner_groups.group_id
-          LEFT JOIN projects group_projects ON group_projects.namespace_id = namespaces.id
+          INNER JOIN ci_runner_groups ON ci_runner_groups.runner_id = ci_runners.id
+          INNER JOIN namespaces ON namespaces.id = ci_runner_groups.group_id
+          INNER JOIN projects group_projects ON group_projects.namespace_id = namespaces.id
         }
       ).where(
         %{