The right clicking context menu path seems to be blocked. I've logged bug PS-26491 "Difficulties deleting a mask attached to a contained layer within a Frame" on your behalf.
In the meantime, select just contained layer. The mask will be selected as well. From the main menu, choose Layer > Layer Mask> Delete.
The right clicking context menu path seems to be blocked. I've logged bug PS-26491 "Difficulties deleting a mask attached to a contained layer within a Frame" on your behalf.
In the meantime, select just contained layer. The mask will be selected as well. From the main menu, choose Layer > Layer Mask> Delete.