Remove pointless version constraint.

--- roman-5.1/pyproject.toml	2025-07-18 06:19:37.000000000 +0100
+++ roman-5.1/pyproject.toml	2025-07-31 16:47:21.889883731 +0100
@@ -4,7 +4,7 @@
 
 [build-system]
 requires = [
-    "setuptools == 78.1.1",
+    "setuptools",
     "wheel",
 ]
 build-backend = "setuptools.build_meta"