Update pyproject.toml to newest conventions

pyproject.toml

@@ -3,6 +3,7 @@ name = "taas_client"
 version = "0.1.0"
 description = ""
 authors = ["ubaumann <github@m.ubaumann.ch>"]
+readme = "README.md"
 
 [tool.poetry.dependencies]
 python = "^3.10"
@@ -18,5 +19,5 @@ pytest = "^7.1.3"
 black = "^22.8.0"
 
 [build-system]
-requires = ["poetry-core>=1.0.0"]
+requires = ["poetry-core"]
 build-backend = "poetry.core.masonry.api"