Remove tasks to be done from onboarding and invite emails

What does this MR do and why?

• first step in removing the tasks to be done feature
  • this is merely the first step, rest are detailed in #424804 (closed)
• with the completion of #418137 (closed), this feature is no longer used in the code

Screenshots or screen recordings

No longer have tasks to be done possible text in the invite/access granted emails as seen in the changes

How to set up and validate locally

Since the feature no longer exists from removal in #424804 (closed), there is no way to really trigger this code naturally except in tests, which can be seen changed in this MR

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #424804 (closed)