feat: removed sequencer rewards command

[keruch]

PR Standards

ADR link https://www.notion.so/dymension/ADR-Whitelisted-Relayer-Fee-Exemption-in-Rollapp-104a4a51f86a80e8ad94c916c87deb17
Closes dymensionxyz/dymension#1226

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After reviewer approval:

• In case PR targets main branch, PR should be squashed and merged.
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[keruch]

@artemijspavlovs MsgCreateSequencer and related messages are to be removed in the RDK repo, so i remove this command as well. Omri asked not to merge it until we release the version, so the PR will be dangling for a while.