fix leak

package.json

 {
   "name": "koishi-plugin-act",
-  "version": "1.0.2",
+  "version": "1.0.3",
   "description": "A plugin playing acts in QQ groups",
   "main": "dist/index.js",
   "dependencies": {

src/playbook/Show.ts

@@ -141,6 +141,9 @@ export class Show {
     }
     clearInterval(this.showInterval);
     this.showInterval = undefined;
+    for (const character of this.playbook.characters) {
+      character.playFun = undefined;
+    }
     this.onFinish(message, this);
     return true;
   }