AlreadyVoting Error - Remove ambiguity (#3280)

This error suggests using either `unvote` or `reap_vote` calls which are
unavailable in the pallet. The only available call for this is
`remove_vote`.

EDIT: Please ignore my earlier write-up. I was able to delegate with
conviction after calling `remove_vote` on all decided proposals

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Co-authored-by: command-bot <>