ci(bigquery): disable two failing tests until WIF auth is worked out

[cpcloud]

No description provided.

[cpcloud]

Still passing locally:

cloud in 🌐 albatross in …/ibis on  disable-failing-bigquery-tests-for-now is 📦 v9.5.0 via 🐍 v3.12.8 via ❄️  impure (ibis-3.12-env)
❯ pytest ibis/backends/bigquery/tests/system/{udf/test_udf_execute,test_client}.py
================================================ test session starts =================================================
platform linux -- Python 3.12.8, pytest-8.3.4, pluggy-1.5.0
benchmark: 5.1.0 (defaults: timer=time.perf_counter disable_gc=False min_rounds=5 min_time=0.000005 max_time=1.0 calibration_precision=10 warmup=False warmup_iterations=100000)
Using --randomly-seed=1437262086
rootdir: /home/cloud/src/github.com/ibis
configfile: pyproject.toml
plugins: xdist-3.6.1, clarity-1.0.1, benchmark-5.1.0, repeat-0.9.3, randomly-3.16.0, pytest_httpserver-1.1.0, timeout-2.3.1, cov-6.0.0, anyio-4.7.0, deadfixtures-2.2.1, mock-3.14.0, hypothesis-6.123.2, snapshot-0.9.0
collected 59 items

ibis/backends/bigquery/tests/system/udf/test_udf_execute.py ..................                                 [ 30%]
ibis/backends/bigquery/tests/system/test_client.py .........................................                   [100%]

=========================================== 59 passed in 202.84s (0:03:22) ===========================================

[tswast]

Thanks