Add an Eq/PartialEq impl for proposal::State (#3861)

Does what it says on the tin; this was just an oversight that this
didn't exist before.

crates/core/component/governance/src/proposal_state.rs

@@ -2,7 +2,7 @@ use serde::{Deserialize, Serialize};
 
 use penumbra_proto::{penumbra::core::component::governance::v1 as pb, DomainType};
 
-#[derive(Debug, Clone, Serialize, Deserialize)]
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
 #[serde(try_from = "pb::ProposalState", into = "pb::ProposalState")]
 pub enum State {
     Voting,