Fix external issue tracker "Issues" link leading to 404s

a70431f874 modified the behavior to link to the external issue tracker
issues URL instead of the project path URL. This restores the
previous behavior.

Closes #21252, #21402

CHANGELOG

@@ -34,6 +34,7 @@ v 8.11.3 (unreleased)
   - Label list shows all issues (opened or closed) with that label
   - Don't show resolve conflicts link before MR status is updated
   - Don't prevent viewing the MR when git refs for conflicts can't be found on disk
+  - Fix external issue tracker "Issues" link leading to 404s
 
 v 8.11.2
   - Show "Create Merge Request" widget for push events to fork projects on the source project. !5978

app/controllers/projects/issues_controller.rb

@@ -212,7 +212,7 @@ class Projects::IssuesController < Projects::ApplicationController
     if action_name == 'new'
       redirect_to external.new_issue_path
     else
-      redirect_to external.issues_url
+      redirect_to external.project_path
     end
   end
 

spec/controllers/projects/issues_controller_spec.rb

@@ -8,13 +8,13 @@ describe Projects::IssuesController do
   describe "GET #index" do
     context 'external issue tracker' do
       it 'redirects to the external issue tracker' do
-        external = double(issues_url: 'https://example.com/issues')
+        external = double(project_path: 'https://example.com/project')
         allow(project).to receive(:external_issue_tracker).and_return(external)
         controller.instance_variable_set(:@project, project)
 
         get :index, namespace_id: project.namespace.path, project_id: project
 
-        expect(response).to redirect_to('https://example.com/issues')
+        expect(response).to redirect_to('https://example.com/project')
       end
     end