fix protobuf-ts generating duplicate imports for everything.

[bluskript]

Currently protobuf-ts generates like this:

import { GiveUpOwnershipResponse } from "./guilds";
import { GiveUpOwnershipRequest } from "./guilds";
import { GrantOwnershipResponse } from "./guilds";
import { GrantOwnershipRequest } from "./guilds";

it should generate like this:

import { GiveUpOwnershipResponse, GiveUpOwnershipRequest, GrantOwnershipResponse, GrantOwnershipRequest } from "./guilds";