Remove Deprecations

[WhiffleFish]

No description provided.

[WhiffleFish]

How do we usually handle this? The current registered POMDPTools version assumes that POMDPs exports all of the POMDPLinter stuff.

So, updating POMDPs breaks POMDPTools in docs and updating POMDPTools breaks the POMDPTools CI as it depends on the current registered version of POMDPs.

Instead of building docs on the current registered version of POMDPTools, do we add it by relative path in docs/make.jl?

Furthermore, the docs depend on POMDPModels.jl which ALSO uses a bunch of deprecated functionality that would be removed.

[zsunberg]

How do we usually handle this?

Just register it without the docs building, then get all the code working correctly, and then create a v1.0.0+docs tag so that the documentation builds and the stable documentation link works.