[issue-4336] halt launch requested notifications on projects

[Tooyosi]

Describe your change here.

Remove launch email notifications from Projects

Review checklist

• [x] First, the most important one: is this PR small enough that you can actually review it? Feel free to just reject a branch if the changes are hard to review due to the length of the diff.
• [ ] If there are any migrations, will they the previous version of the app work correctly after they've been run (e.g. the don't remove columns still known about by ActiveRecord).
• [ ] If anything changed with regards to the public API, are those changes also documented in the apiary.apib file?
• [x] Are all the changes covered by tests? Think about any possible edge cases that might be left untested.

[lcjohnso]

Looks good to me; accomplishes the goal to remove the project launch_requested change mailer.