fix: use immutable update for comment vote state

[GeoSyntax]

What changed

• Replace direct object mutation with spread operator in submitVoteComment for immutable state update

Why

• The current code directly mutates the item object inside comments.map(), which violates React's immutable update principle
• The child component ActionBar is wrapped with React.memo, direct mutation may prevent memo from detecting changes, causing potential rendering issues

Before

item.vote_count = is_cancel ? item.vote_count - 1 : item.vote_count + 1;
item.is_vote = !is_cancel;
return item;

After

return {
  ...item,
  vote_count: is_cancel ? item.vote_count - 1 : item.vote_count + 1,
  is_vote: !is_cancel,
};

Testing

• Vote / unvote on comments works correctly
• Vote after pagination works correctly
• Data is correct after page refresh