Keep only the bot cookie for the last visited bot

A workspace conversation is never remembered, so /admin/bots always
reopens the bot's own chat.

src/functions/server/with-last-visited-bot-cookies.ts

@@ -6,30 +6,20 @@ type Params = {
     req: Request;
     res: Response;
     bot_id: number | string;
-    /**
-     * Null or undefined: the bot's own chat.
-     */
-    workspace_id?: number | string | null;
 };
 
 /**
- * The page's response with the last-visited cookies set, so `/admin/bots`
- * opens this conversation again next time. Called from the conversation
+ * The page's response with the last-visited cookie set, so `/admin/bots`
+ * opens this bot's own chat again next time. Called from the conversation
  * pages' `res_transform`, which is why it takes and returns the response.
  */
-export default function withLastVisitedBotCookies({
-    req,
-    res,
-    bot_id,
-    workspace_id,
-}: Params): Response {
+export default function withLastVisitedBotCookies({ req, res, bot_id }: Params): Response {
     const new_res = res.clone();
 
     setCookies(
         new_res,
         lastVisitedBotCookies({
             bot_id,
-            workspace_id,
             secure: isSecureRequest({ req }),
         }),
     );