Update one fixture to PEP-621 style pyproject.toml

So we have fixtures testing both the new and old style config.

spec/fixtures/poetry_basic/pyproject.toml

@@ -1,10 +1,14 @@
+[project]
+name = "poetry-basic"
+version = "0.0.0"
+requires-python = ">=3.13"
+dependencies = [
+    "typing-extensions"
+]
+
 [tool.poetry]
 package-mode = false
 
-[tool.poetry.dependencies]
-python = "^3.13"
-typing-extensions = "*"
-
 # This group shouldn't be installed due to us passing `--only main`.
-[tool.poetry.group.test.dependencies]
+[tool.poetry.group.dev.dependencies]
 pytest = "*"

spec/hatchet/poetry_spec.rb

@@ -63,7 +63,7 @@
   end
 
   context 'when the Poetry and Python versions have changed since the last build' do
-    let(:buildpacks) { ['https://github.com/heroku/heroku-buildpack-python#v274'] }
+    let(:buildpacks) { ['https://github.com/heroku/heroku-buildpack-python#v275'] }
     let(:app) { Hatchet::Runner.new('spec/fixtures/poetry_basic', buildpacks:) }
 
     it 'clears the cache before installing' do
@@ -76,7 +76,7 @@
           remote: -----> Using Python 3.13 specified in .python-version
           remote: -----> Discarding cache since:
           remote:        - The Python version has changed from 3.13.1 to #{LATEST_PYTHON_3_13}
-          remote:        - The Poetry version has changed from 1.8.5 to #{POETRY_VERSION}
+          remote:        - The Poetry version has changed from 2.0.1 to #{POETRY_VERSION}
           remote: -----> Installing Python #{LATEST_PYTHON_3_13}
           remote: -----> Installing Poetry #{POETRY_VERSION}
           remote: -----> Installing dependencies using 'poetry sync --only main'