docs: remove deprecations guide, no longer relevant in Mongoose 7

[vkarpov15]

Summary

This guide is no longer relevant in Mongoose 7 as was mentioned in #13547

Examples

[hasezoey]

if it is just currently not relevant anymore, how about repurposing it as a general deprecation notice instead of just mongodb driver deprecations? (a replacement to the wiki, which seems to not be actively used anymore)

and while there is nothing to list just say that there is nothing to list (yet)?

[vkarpov15]

Given that there's nothing to list right now, I think we should err on the side of removing this page. We can always add it back once we have something to list.

[hasezoey]

Given that there's nothing to list right now, I think we should err on the side of removing this page. We can always add it back once we have something to list.

also sounds good to me

PS: i have hidden the duplicate messages that seem to be there by accident

[IslandRhythms]

LGTM

[Uzlopak]

LGTM

[hasezoey]

i actually think now that #13572 has been merged, there is a reason to still have the deprecation file, mentioning that findOneAndUpdate option overwrite is deprecated and findOneAndReplace should be used instead

[vkarpov15]

Good point @hasezoey , I'll close this and create a new PR to remove the contents of the current deprecation guide and instead add the overwrite deprecation there once we have that.