Exclude files from PyPI release

PiperOrigin-RevId: 516496220

Author: Conchylicultor

pyproject.toml

@@ -54,5 +54,11 @@ pyink-indentation = 2
 pyink-use-majority-quotes = true
 
 [build-system]
-requires = ["flit_core >=3.5,<4"]
+requires = ["flit_core >=3.8,<4"]
 build-backend = "flit_core.buildapi"
+
+[tool.flit.sdist]
+exclude = [
+  # Do not release tests files on PyPI
+  "**/*_test.py",
+]