Update: This change was accepted upstream

Change the ppd in /etc/cups/ppd/HP_Color_LaserJet_CP1215.ppd to have:

*HWMargins: 18.00 14.40 18.00 14.40

Mine was formerly:

*HWMargins: 12.00 12.00 12 12

Once it’s updated, restart cups and re-add the printer.