fix!: remove GovPreventSpamDecorator

[mpoke]

Description

Closes: #2911

Remove GovPreventSpamDecorator as this logic is already implemented in SDK 0.47, see https://github.com/cosmos/cosmos-sdk/blob/v0.47.8/x/gov/keeper/msg_server.go#L32.

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Author Checklist

All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.

I have...

• Included the correct type prefix in the PR title
• Added ! to the type prefix if API, client, or state breaking change (i.e., requires minor or major version bump)
• Targeted the correct branch (see PR Targeting)
• Provided a link to the relevant issue or specification
• Followed the guidelines for building SDK modules
• Included the necessary unit and integration tests
• Added a changelog entry in .changelog (for details, see contributing guidelines)
• Included comments for documenting Go code
• Updated the relevant documentation or specification
• Reviewed "Files changed" and left comments if necessary
• Confirmed all CI checks have passed

Reviewers Checklist

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your handle next to the items reviewed if you only reviewed selected items.

I have...

• confirmed the correct type prefix in the PR title
• confirmed ! in the type prefix if API or client breaking change
• confirmed all author checklist items have been addressed
• reviewed state machine logic
• reviewed API design and naming
• reviewed documentation is accurate
• reviewed tests and test coverage

[MSalopek]

Don't remap errors, other than that LGTM

[MSalopek]

LGTM!

Please appease linter before merge.

[sainoe]

LGTM. Thanks!