fix(docs): Fix UI port in E2E docs (#22881)

Signed-off-by: Oliver Gondža <[email protected]>

Author: olivergondza

docs/developer-guide/test-e2e.md

@@ -22,7 +22,7 @@ Git repository via file url: `file:///tmp/argo-e2e***`.
 1. Start the e2e version `make start-e2e`
 2. Run the tests: `make test-e2e`
 
-You can observe the tests by using the UI [http://localhost:8080/applications](http://localhost:8080/applications) with username `"admin"` and password `"password"`.
+You can observe the tests by using the UI [http://localhost:4000/applications](http://localhost:4000/applications) with username `"admin"` and password `"password"`.
 
 ## Configuration of E2E Tests execution