This took longer than usual to arrive for whatever reason, with the stable Android 15 QPR1 release widely rolling out last week. The OTA is for users that exited the Android Beta Program to avoid QPR2, though that's been pretty stable with the added benefit of features like the Modes redesign and Notification Cooldown.
On a Pixel Fold, it's just a 10.48 MB update that takes users to the December 2024 security patch. Installing this will not wipe any user data.
Go to Settings > System > Software updates > System update and confirm "Android Beta Exit No Data Wipe" before installing.