Demote unstable tests (#29250)

* [skip ci] Demote unstable tests
* [skip ci] Further demotions, fix artifact jumbling

e2e-tests/cypress/tests/integration/channels/integrations/incoming_webhook/attachment_does_not_collapse_spec.ts

@@ -7,7 +7,6 @@
 // - Use element ID when selecting an element. Create one if none.
 // ***************************************************************
 
-// Stage: @prod
 // Group: @channels @incoming_webhook
 
 describe('Integrations/Incoming Webhook', () => {