pyproject: fix source-include for tests in sdists (#397)

Author: woodruffw

pyproject.toml

@@ -3,7 +3,7 @@ requires = ["uv_build>=0.9.6,<0.10.0"]
 build-backend = "uv_build"
 
 [tool.uv.build-backend]
-source-include = ["tests/"]
+source-include = ["tests/**"]
 module-name = "cachecontrol"
 module-root = ""