lqt: make transaction planner request take only a single denom (#5091)

## Describe your changes

Looking at the ongoing integration work in:
penumbra-zone/web#2041, the transaction planner
request for lqt votes can only make use of a single incentivized denom
anyways, which is what we want to support in the final ux, so having a
repeated field here that subsequently gets truncated to the first
provided value is superfluous. This change makes the field plain
instead.

This can be tested inside of that PR.

## Issue ticket number and link

## Checklist before requesting a review

- [x] I have added guiding text to explain how a reviewer should test
these changes.

- [x] If this code contains consensus-breaking changes, I have added the
"consensus-breaking" label. Otherwise, I declare my belief that there
are not consensus-breaking changes, for the following reason:

  > Affects clients only.

crates/proto/src/gen/penumbra.view.v1.rs

@@ -803,8 +803,8 @@ pub mod transaction_planner_request {
     #[derive(Clone, PartialEq, ::prost::Message)]
     pub struct ActionLiquidityTournamentVote {
         /// The asset the user wants to vote for.
-        #[prost(message, repeated, tag = "1")]
-        pub incentivized: ::prost::alloc::vec::Vec<
+        #[prost(message, optional, tag = "1")]
+        pub incentivized: ::core::option::Option<
             super::super::super::core::asset::v1::Denom,
         >,
         /// The address the user wants potential rewards to go to.

crates/proto/src/gen/penumbra.view.v1.serde.rs

@@ -7847,7 +7847,7 @@ impl serde::Serialize for transaction_planner_request::ActionLiquidityTournament
     {
         use serde::ser::SerializeStruct;
         let mut len = 0;
-        if !self.incentivized.is_empty() {
+        if self.incentivized.is_some() {
             len += 1;
         }
         if self.rewards_recipient.is_some() {
@@ -7860,8 +7860,8 @@ impl serde::Serialize for transaction_planner_request::ActionLiquidityTournament
             len += 1;
         }
         let mut struct_ser = serializer.serialize_struct("penumbra.view.v1.TransactionPlannerRequest.ActionLiquidityTournamentVote", len)?;
-        if !self.incentivized.is_empty() {
-            struct_ser.serialize_field("incentivized", &self.incentivized)?;
+        if let Some(v) = self.incentivized.as_ref() {
+            struct_ser.serialize_field("incentivized", v)?;
         }
         if let Some(v) = self.rewards_recipient.as_ref() {
             struct_ser.serialize_field("rewardsRecipient", v)?;
@@ -7954,7 +7954,7 @@ impl<'de> serde::Deserialize<'de> for transaction_planner_request::ActionLiquidi
                             if incentivized__.is_some() {
                                 return Err(serde::de::Error::duplicate_field("incentivized"));
                             }
-                            incentivized__ = Some(map_.next_value()?);
+                            incentivized__ = map_.next_value()?;
                         }
                         GeneratedField::RewardsRecipient => {
                             if rewards_recipient__.is_some() {
@@ -7982,7 +7982,7 @@ impl<'de> serde::Deserialize<'de> for transaction_planner_request::ActionLiquidi
                     }
                 }
                 Ok(transaction_planner_request::ActionLiquidityTournamentVote {
-                    incentivized: incentivized__.unwrap_or_default(),
+                    incentivized: incentivized__,
                     rewards_recipient: rewards_recipient__,
                     staked_notes: staked_notes__.unwrap_or_default(),
                     epoch_index: epoch_index__.unwrap_or_default(),

proto/penumbra/penumbra/view/v1/view.proto

@@ -445,7 +445,7 @@ message TransactionPlannerRequest {
 
   message ActionLiquidityTournamentVote {
     // The asset the user wants to vote for.
-    repeated core.asset.v1.Denom incentivized = 1;
+    core.asset.v1.Denom incentivized = 1;
     // The address the user wants potential rewards to go to.
     core.keys.v1.Address rewards_recipient = 2;
     // The note containing the staked note used for voting.
@@ -875,4 +875,4 @@ message LatestSwapsResponse {
   uint64 block_height = 4;
   // The hash of the transaction that was broadcast.
   core.txhash.v1.TransactionId id = 5;
-}
+}