Revert "Allow poetry-core 1.5.0 (#14949)"

This reverts commit 64a631879c.

pyproject.toml

@@ -127,9 +127,7 @@ exclude = [
     { path = "synapse/*.so", format = "sdist"}
 ]
 
-[tool.poetry.build]
-script = "build_rust.py"
-generate-setup-file = true
+build = "build_rust.py"
 
 [tool.poetry.scripts]
 synapse_homeserver = "synapse.app.homeserver:main"
@@ -352,7 +350,7 @@ towncrier = ">=18.6.0rc1"
 # system changes.
 # We are happy to raise these upper bounds upon request,
 # provided we check that it's safe to do so (i.e. that CI passes).
-requires = ["poetry-core>=1.0.0,<=1.5.0", "setuptools_rust>=1.3,<=1.5.2"]
+requires = ["poetry-core>=1.0.0,<=1.3.2", "setuptools_rust>=1.3,<=1.5.2"]
 build-backend = "poetry.core.masonry.api"