remove xtensor version upper bound, set howardhinnant_date upper bound

[KrisThielemans]

No description provided.

[KrisThielemans]

@johnstairs @naegelejd I get https://github.com/ETSInitiative/PETSIRD/actions/runs/22763081810/job/66024087418?pr=184#step:9:53

/usr/share/miniconda/envs/yardl/bin/ccache /usr/share/miniconda/envs/yardl/bin/x86_64-conda-linux-gnu-c++ -DHAS_STRING_VIEW=1 -DONLY_C_LOCALE=0  -fvisibility-inlines-hidden -fmessage-length=0 -march=nocona -mtune=haswell -ftree-vectorize -fPIC -fstack-protector-strong -fno-plt -O2 -ffunction-sections -pipe -isystem /usr/share/miniconda/envs/yardl/include -std=gnu++20 -Wall -Wextra -pedantic -MD -MT generated/petsird/CMakeFiles/petsird_generated.dir/ndjson/protocols.cc.o -MF generated/petsird/CMakeFiles/petsird_generated.dir/ndjson/protocols.cc.o.d -o generated/petsird/CMakeFiles/petsird_generated.dir/ndjson/protocols.cc.o -c /home/runner/work/PETSIRD/PETSIRD/cpp/generated/petsird/ndjson/protocols.cc
In file included from /home/runner/work/PETSIRD/PETSIRD/cpp/generated/petsird/ndjson/protocols.cc:3:
/home/runner/work/PETSIRD/PETSIRD/cpp/generated/petsird/ndjson/../yardl/detail/ndjson/serializers.h: In static member function 'static void nlohmann::json_abi_v3_12_0::adl_serializer<std::chrono::duration<long int, std::ratio<1, 1000000000> > >::from_json(const nlohmann::json_abi_v3_12_0::ordered_json&, yardl::Time&)':
/home/runner/work/PETSIRD/PETSIRD/cpp/generated/petsird/ndjson/../yardl/detail/ndjson/serializers.h:148:22: error: no matching function for call to 'parse(const char [3], yardl::Time&)'
  148 |     ss >> date::parse("%T", value);
      |           ~~~~~~~~~~~^~~~~~~~~~~~~

In this PR. That's weird, as I only changed the xtensor dependency, but possibly it got a new version of data. See microsoft/yardl#245