docs: fix "empty array" meson syntax
On recent versions of Meson (0.47+) these are synonymous, but we still support older versions than that, so let's use the correct syntax to avoid confusing users of old Meson versions.
On recent versions of Meson (0.47+) these are synonymous, but we still support older versions than that, so let's use the correct syntax to avoid confusing users of old Meson versions.