[1.9] Set due dates for docs/relnotes/marketing dependencies about sig-release

[Bradamant3]

cc @idvoretskyi who helped with themes in relnotes for 1.8. I'll ping on Slack also. cc @nickchase who's helping with relnotes especially the script for generating. I need to dig some more to find where information for "feature related relnotes" might come from. (Came from pestering individual sigs for 1.8)
Blog post and talking points come from marketing. @nwoods3 do you need help here?

[nwoods3]

@Bradamant3 re: blog post and talking points - Yes, I will need the release team's help and Aparna has been a big help on these for the last several releases too. I am updating the marketing plan we used for 1.8 for 1.9 and will send that around to the release team on Monday, 10/30. The plan will have a timeline for the blog and talking points. We can discuss on the next release team call and I can answer any questions. The blog and talking points will not really come together under after the code freeze. I recommend we hold a messaging discussion around this time to solidify what we want to say in the blog and talking points.