Update mentoring team slack channel on Contribute by Mentoring page

Page location/URL

https://www.drupal.org/community/contributor-guide/contribution-areas/me...

Problem/Motivation

Slack channel was renamed from #mentoring-team to #mentoring-team-coordination

Proposed resolution

Channel names are up-to-date on the page:

- "Join the #mentoring-team-coordination channel on Drupal Slack"
- "We hold a meeting to organize mentoring efforts at various events once a month on the second Wednesday at 20:00 UTC in #mentoring-team-coordination on Slack. (what time is that for me?)"

Remaining tasks