Remove redundant "Managing dev guide release" section from Editors chapter

[mpadge]

https://devguide.ropensci.org/editorguide.html#bookrelease - that's now all in separate appendix

[maelle]

what's redundant? that section links to the checklist

[mpadge]

I'm not sure anymore, but i think back then i was more thinking that that section is a bit out-of-place in that chapter, and that docs for dev guide stuff would ultimately end up somewhere else? But feel free to close and ignore anyway, if that's easier for now 😄