Don't tell to the user to ask to join the matrix room

because we already ask his matrix username in the issue template

.github/workflows/add-instance-updown.yml

@@ -83,10 +83,6 @@ jobs:
                       '- Improving the performance and the stability of your public instance: https://docs.invidious.io/improve-public-instance/',
                       '',
                       'It is highly recommended to follow these tutorials because it will allow the instance to stay stable and performant over the long term.',
-                      '',
-                      'Please consider joining the Matrix room for public instance maintainers by joining our Matrix room: https://matrix.to/#/#invidious:matrix.org',
-                      'then pinging @ unixfox, @ TheFrenchGhosty and @ SamantazFox for asking to be invited to the Matrix room.',
-                      'We discuss troubles managing a public instance, sharing some advices and more.'
                       ].join('\n');
                     await github.rest.issues.createComment({
                       issue_number: context.issue.number,