Bump: 'fermyon:spin/postgres@3.0.0' interface

[tyler-harpool]

Currently postgres@2.0.0 is supported but not 3.0.

failed to instantiate spin-test composition
Caused by: component imports instance spin:postgres/postgres@3.0.0, but a matching implementation was not found in the linker
Caused by: instance export connection has the wrong type
Caused by: resource implementation is missing

By supporting 3.0.0 we can run spin test with pg3 compatibility.

spin-test/host-wit/deps/spin-test-virt/world.wit

Line 11 in 593860b

export fermyon:spin/postgres@2.0.0;