chore: remove unused type ServerTokenResponse (#788)

After this commit[1], type `ServerTokenResponse` became unused, remove
it as well.

[1]: 57ab08fb6d

src/commands/servers.ts

@@ -1,7 +1,6 @@
 import { invoke } from "@tauri-apps/api/core";
 
 import {
-  ServerTokenResponse,
   Server,
   Connector,
   DataSource,

src/types/commands.ts

@@ -1,7 +1,3 @@
-export interface ServerTokenResponse {
-  access_token?: string;
-}
-
 interface Provider {
   name: string;
   icon: string;