graphics/vulkan-validation-layers: pacify check-plist after 100f2890786b

> Checking for pkg-plist issues (check-plist)

> Parsing plist

> Checking for items in STAGEDIR missing from pkg-plist

Error: Orphaned: @dir include/vulkan/external/vma

> Checking for items in pkg-plist which are not in STAGEDIR

> Error: Plist issues found.

• Error code 1