ceph: hack-fix build

We surely don't need docs in the overridden pyopenssl.
https://hydra.nixos.org/build/287563868/nixlog/1/tail

pkgs/tools/filesystems/ceph/default.nix

···
   nasm,
   pkg-config,
   which,
+  openssl,
 
   # Tests
   nixosTests,
···
           propagatedBuildInputs = old.propagatedBuildInputs or [ ] ++ [
             self.flaky
           ];
+          # hack: avoid building docs due to incompatibility with current sphinx
+          nativeBuildInputs = [ openssl ]; # old.nativeBuildInputs but without sphinx*
+          outputs = lib.filter (o: o != "doc") old.outputs;
         });
 
         # This is the most recent version of `trustme` that's still compatible with `cryptography` 40.