fix(scipy): allow rounding differences in STFT tests

Keep STFT tests enabled with precision-appropriate tolerances for
x86-64-v3 builds. Add the override under overlays/patches/scipy and
remove the commented-out test exclusions.

overlays/patches/default.nix

@@ -1,3 +1,9 @@
 _final: prev: {
   gnutls = import ./gnutls { inherit (prev) gnutls; };
+
+  pythonPackagesExtensions = prev.pythonPackagesExtensions ++ [
+    (_pythonFinal: pythonPrev: {
+      scipy = import ./scipy { inherit (pythonPrev) scipy; };
+    })
+  ];
 }