runtime-api: remove redundant version checks (#7610)

## Issue
- [[#1940] Cleanup boilerplate code when DisabledValidators runtime api
call is
released](https://github.com/paritytech/polkadot-sdk/issues/1940)
- Includes other runtime APIs, such as `MinimumBackingVotes` and
`NodeFeatures`, that are already supported by Polkadot.

## Description
This PR removes unnecessary runtime API version checks from
`subsystem-util/src/runtime` for APIs supported by Polkadot (the most
recent network to upgrade). Specifically, it applies to the
`DisabledValidators`, `MinimumBackingVotes` and `NodeFeatures` APIs.

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Co-authored-by: Bastian Köcher <git@kchr.de>