python: don't use keep for hooks, so they will be spliced

as far as i can see there should be no reason to not splice the hooks

wrapPython for some reason has to be not spliced because 'substitutions.pythonHost = python;' causes
```
error: output '/nix/store/li07bad6s9brxx7cf8j408631nca39ka-python3.10-chardet-5.1.0-aarch64-unknown-linux-gnu' is not allowed to refer to the following paths:
         /nix/store/fdqpyj613dr0v1l1lrzqhzay7sk4xg87-python3-3.10.10
```

ericson said in NixOS#104201 (comment) that the reason they were in keep was to not splice them but before the commit which broke hook splicing (33d12e5) everything appeared to be working correctly when cross-compiling

we also somehow get a correctly spliced python in nativeBuildInputs for free

pkgs/development/interpreters/python/passthrufun.nix

@@ -47,7 +47,7 @@
         selfTargetTarget = pythonOnTargetForTarget.pkgs or {}; # There is no Python TargetTarget.
       };
       hooks = import ./hooks/default.nix;
-      keep = self: hooks self {};
+      keep = self: { inherit (self) wrapPython; };
       optionalExtensions = cond: as: lib.optionals cond as;
       pythonExtension = import ../../../top-level/python-packages.nix;
       python2Extension = import ../../../top-level/python2-packages.nix;