For future reference, (assuming XPosed was the only system modification you did) all you needed to do was to open XPosed framework app, go to settings in that app, and click the uninstall button (that would restore the system file that was modified by XPosed installation. Do not uninstall XPosed app itself). Then, you could download the OTA zip file to your phone, and flash it in your custom recovery.Didn't work for me. I'm stock but I have Xposed Framework on the system. The OTA showed up but it would install. I gave up and installed the factory image directly.
It might also not work if you have disabled any of the stock apps.