[koa-session] types were overwriting a Class with an interface FIX (#36206)

* koa-session was overwriting a Class with an interface

* forgot semicolons

types/koa-session/index.d.ts

@@ -205,11 +205,6 @@ declare module "koa" {
         session: session.Session | null;
         readonly sessionOptions: session.opts | undefined;
     }
-
-    interface Application {
-        on(name: "session:missed" | "session:expired" | "session:invalid", data: { key?: string, value?: Partial<session.Session>, ctx: Context }): void;
-        once(name: "session:missed" | "session:expired" | "session:invalid", data: { key?: string, value?: Partial<session.Session>, ctx: Context }): void;
-    }
 }
 
 export = session;

types/koa-session/koa-session-tests.ts

@@ -40,10 +40,18 @@ app.use(session({
     path: "/",
 }, app));
 
+// can still use koa-session events, although without autocomplete
+app.on('session:missed', () => {});
+app.on('session:expired', () => {});
+app.on('session:invalid', () => {});
+
 app.use((ctx, next) => {
     // reset the session
     ctx.session = null;
 
+    // does not interfere with Application->EventEmitter #32389
+    ctx.app.emit('error', new Error('this is an user-generated Error'));
+
     return next();
 });