Uncheck "Goods Receipt" on Purchase Order

Hello Experts,

please, how is it possible on Purchase Order / Delivery Tab to uncheck field "Goods Receipt"? This field was checked by mistake and now it is grey in ME22N.

Because it is checked now it is not possible to post the invoice in MIRO (no items available for posting, since actually for this PO no goods recept will be done).

Thank you,

Ondrej