Demote unstable tests from daily run (#29147)

* Demote unstable tests from daily run

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

e2e-tests/cypress/tests/integration/channels/plugins/demo_plugin/webhook_spec.js

@@ -7,7 +7,6 @@
 // - Use element ID when selecting an element. Create one if none.
 // ***************************************************************
 
-// Stage: @prod
 // Group: @channels @plugin @not_cloud
 
 import * as TIMEOUTS from '../../../../fixtures/timeouts';

e2e-tests/cypress/tests/integration/channels/plugins/plugin_startup_fail_spec.js

@@ -14,7 +14,6 @@
  * under fixtures folder.
  */
 
-// Stage: @prod
 // Group: @channels @system_console @plugin @not_cloud @timeout_error
 
 import * as TIMEOUTS from '../../../fixtures/timeouts';