SIMPLE-6506 removed/deprecated offline mode leftovers

[daniel-valent]

These things are unused and unnecessary, will have no new users if kept for a bit longer (since they have no use) and are not worth the effort of deprecating in two phases. Because of that, I skipped deprecating while keeping functionality and outright removed the functionality. This means that this should not go into 2.7.1.

[tulus42]

I guess when we call it "deprecated" it should still work for a while. Handling removed parameter to tell users it was removed is not a bad idea, but maybe don't call it deprecated. Or remove it completly and make it clear in the docs/release notes.