Fix remaining deprecated pixi project -> workspace

Author: ctrueden

src/test/resources/envs/cowsay-pixi-pyproject.toml

@@ -3,7 +3,7 @@ name = "cowsay-pixi-test"
 version = "0.1.0"
 description = "Test project for cowsay with Pixi using pyproject.toml"
 
-[tool.pixi.project]
+[tool.pixi.workspace]
 channels = ["conda-forge"]
 platforms = ["linux-64", "osx-64", "osx-arm64", "win-64"]