[REG-1774] Update documentation about legacy input manager support

[svolokh]

This PR removes disclaimers about not supporting playback for the legacy input manager in the docs (with the last PR merged today in RGUnityBots, we now have feature parity for playback for the new and old input systems). There were no other limitations listed in the "Known Limitations" section, so I've renamed this to "Feedback" for now.

However, for now we are still using the new input system for capturing inputs, so it is still true that the package will install the new input system package even if the legacy input manager is in use, so I've left those statements in.

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Find the pull request instructions here

Every reviewer and the owner of the PR should consider these points in their request (feel free to copy this checklist so you can fill it out yourself in the overall PR comment)

• The code is extensible and backward compatible
• New public interfaces are extensible and open to backward compatibility in the future
• If preparing to remove a field in the future (i.e. this PR removes an argument), the argument stays but is no longer functional, and attaches a deprecation warning. A linear task is also created to track this deletion task.
• Non-critical or potentially modifiable arguments are optional
• Breaking changes and the approach to handling them have been verified with the team (in the Linear task, design doc, or PR itself)
• The code is easy to read
• Unit tests are added for expected and edge cases
• Integration tests are added for expected and edge cases
• Functions and classes are documented
• Migrations for both up and down operations are completed
• A documentation PR is created and being reviewed for anything in this PR that requires knowledge to use
• Implications on other dependent code (i.e. sample games and sample bots) is considered, mentioned, and properly handled
• Style changes and other non-blocking changes are marked as non-blocking from reviewers