Disable some user warnings in tests

[yaelbh]

test/unit/test_sampler.py::TestSamplerV2::test_run_program_inputs_3
  /mnt/wsl/runtime/pvalrzz/qiskit_ibm_runtime/utils/validations.py:40: UserWarning: The 1-th circuit has no output classical registers so the result will be empty. Did you mean to add measurement instructions?
    warnings.warn(

test/unit/test_sampler.py::TestSamplerV2::test_rzz_angle_validation_2_1
  /root/miniforge3/envs/env1/lib/python3.12/site-packages/qiskit/primitives/backend_sampler_v2.py:139: UserWarning: The 0-th pub's circuit has no output classical registers and so the result will be empty. Did you mean to add measurement instructions?
    warnings.warn(

As far as I see, we are fine with these circuits not performing any measurements. So, either we suppress these warnings, or we add measure instructions just to make the warning silent.