Be less aggressive with killing services

What does this Merge Request do and why?

In !2033 (merged) we sent a kill -9 to a service after a 'polite' kill was requested, this resulted in more zombie runsv processes than before 😞 The main culprit prior to !2033 (merged) was the rails-background-jobs zombie process which should be fixed with !2077 (merged).

In this MR, we remove sending the kill -9 for all services.

Closes: #1269 (closed)

Merge Request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise Issue to follow-up.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.