devel/py-click-aliases: Fix BUILD_DEPENDS

from pyproject.toml:
[build-system]
requires = ["poetry-core"]
build-backend = "poetry.core.masonry.api"

Approved by: portmgr (blanket)
With hat: python
Reference: https://github.com/click-contrib/click-aliases/blob/v1.0.4/pyproject.toml#L24-L26