feat: add support for Python 3.14

[parthea]

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[parthea]

Blocked on geopandas/pyogrio#560

Collecting pyogrio>=0.7.2 (from geopandas>=0.12.2->bigframes==2.28.0)
  Downloading pyogrio-0.11.1.tar.gz (287 kB)
  Installing build dependencies: started
  Installing build dependencies: finished with status 'done'
  Getting requirements to build wheel: started
  Getting requirements to build wheel: finished with status 'done'
  Preparing metadata (pyproject.toml): started
  Preparing metadata (pyproject.toml): finished with status 'error'
  error: subprocess-exited-with-error
  
  × Preparing metadata (pyproject.toml) did not run successfully.

[shuoweil]

please do not remove pytest.mark.skipif() for these two tests