test_irods_key_value_proxy.cpp ignores return value of nodiscard function std::begin

[SwooshyCueb]

test_irods_key_value_proxy.cpp ignores the return value of std::begin, which causes a compilation error when building against libstdc++ 13, due to nodiscard.

irods/unit_tests/src/test_irods_key_value_proxy.cpp

Line 567 in e4b4e8a

std::begin(proxy);