refactor(frontend): simplify default expiration date handling in APIKeyCredentialsModal

### Changes
- Removed the `getDefaultExpirationDate` function and set the `expiresAt` default value to an empty string in the `useAPIKeyCredentialsModal` hook. This change streamlines the code by eliminating unnecessary complexity related to date handling.

### Impact
- Enhances code readability and maintainability by simplifying the default value assignment for expiration dates.

autogpt_platform/frontend/src/components/contextual/CredentialsInput/components/APIKeyCredentialsModal/useAPIKeyCredentialsModal.ts

@@ -40,24 +40,12 @@ export function useAPIKeyCredentialsModal({
     expiresAt: z.string().optional(),
   });
 
-  function getDefaultExpirationDate(): string {
-    const tomorrow = new Date();
-    tomorrow.setDate(tomorrow.getDate() + 1);
-    tomorrow.setHours(0, 0, 0, 0);
-    const year = tomorrow.getFullYear();
-    const month = String(tomorrow.getMonth() + 1).padStart(2, "0");
-    const day = String(tomorrow.getDate()).padStart(2, "0");
-    const hours = String(tomorrow.getHours()).padStart(2, "0");
-    const minutes = String(tomorrow.getMinutes()).padStart(2, "0");
-    return `${year}-${month}-${day}T${hours}:${minutes}`;
-  }
-
   const form = useForm<APIKeyFormValues>({
     resolver: zodResolver(formSchema),
     defaultValues: {
       apiKey: "",
       title: "",
-      expiresAt: getDefaultExpirationDate(),
+      expiresAt: "",
     },
   });