Remove RFC-0759 ram-bundle command from cli (#43292)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/43292

The ram-bundle command isn't necessary now that Hermes is our default VM.  The RFC specifically calls for the CLI command to be removed [1].

[1] https://github.com/react-native-community/discussions-and-proposals/blob/main/proposals/0759-react-native-frameworks.md#commands-to-be-removed

Changelog:
[General][Removed] - RFC-0759 remove ram-bundle command.

Reviewed By: NickGerleman, cipolleschi

Differential Revision: D54430289

fbshipit-source-id: 49d519c007b739f89ffe9032fec905c56ea49f4a