Remove deprecations for 0.19

[stewSquared]

Resolves #1330

PR Checklist (not all items are relevant to all PRs)

• [ ] ~Added unit-tests (for runtime code)~
• [ ] ~Added bootstrapped code + smoke tests (when the rendering logic is modified)~
• [ ] ~Added build-plugins integration tests (when reflection loading is required at codegen-time)~
• [ ] ~Added alloy compliance tests (when simpleRestJson protocol behaviour is expanded/updated)~
• [ ] ~Updated dynamic module to match generated-code behaviour~
• [ ] ~Added documentation~
• [ ] Updated changelog

I imagine updating the changelog is unnecessary if the deprecations were previously mentioned.

[CLAassistant]

All committers have signed the CLA.

[kubukoz]

Normally I'd only get to such tasks once we're relatively close to that 0.19 release, but it doesn't hurt so let's go with it :)