[Fix] Hardcode dependency to pre-release mpython-core

Author: johmedr

pyproject.toml

@@ -26,7 +26,7 @@ classifiers = [
 ]
 dependencies = [
     "numpy", 
-    "mpython-core<=25.4"
+    "mpython-core<=25.4a3"
 ]
 
 [project.urls]