perf: remove an unnecessary extra dry_run query from read_gbq_table

[tswast]

Also, removes some unnecessary warnings from SQL Cell code paths.

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Fixes internal issue 437090788 🦕

[tswast]

presubmit failure:

________________________ test_skip_bq_connection_check _________________________ [gw6] linux -- Python 3.12.7 /tmpfs/src/github/python-bigquery-dataframes/.nox/system-3-12/bin/python args = (parent: "projects/bigframes-dev/locations/us-central1" function { name: "projects/bigframes-dev/locations/us-centra...: ALLOW_INTERNAL_ONLY available_memory: "1024Mi" } } function_id: "bigframes-065f0771cfb5054c019833f3812398d3" ,) kwargs = {'metadata': [('x-goog-request-params', 'parent=projects/bigframes-dev/locations/us-central1'), ('x-goog-api-client', 'bigframes/2.14.0 ibis/9.2.0 gl-python/3.12.7 grpc/1.74.0 gax/2.25.1')]} @functools.wraps(callable_) def error_remapped_callable(*args, **kwargs): try: > return callable_(*args, **kwargs) [.nox/system-3-12/lib/python3.12/site-packages/google/api_core/grpc_helpers.py:76](https://cs.corp.google.com/piper///depot/google3/.nox/system-3-12/lib/python3.12/site-packages/google/api_core/grpc_helpers.py?l=76): _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ [.nox/system-3-12/lib/python3.12/site-packages/grpc/_interceptor.py:277](https://cs.corp.google.com/piper///depot/google3/.nox/system-3-12/lib/python3.12/site-packages/grpc/_interceptor.py?l=277): in __call__ response, ignored_call = self._with_call( [.nox/system-3-12/lib/python3.12/site-packages/grpc/_interceptor.py:332](https://cs.corp.google.com/piper///depot/google3/.nox/system-3-12/lib/python3.12/site-packages/grpc/_interceptor.py?l=332): in _with_call return call.result(), call [.nox/system-3-12/lib/python3.12/site-packages/grpc/_channel.py:440](https://cs.corp.google.com/piper///depot/google3/.nox/system-3-12/lib/python3.12/site-packages/grpc/_channel.py?l=440): in result raise self [.nox/system-3-12/lib/python3.12/site-packages/grpc/_interceptor.py:315](https://cs.corp.google.com/piper///depot/google3/.nox/system-3-12/lib/python3.12/site-packages/grpc/_interceptor.py?l=315): in continuation response, call = self._thunk(new_method).with_call( [.nox/system-3-12/lib/python3.12/site-packages/grpc/_channel.py:1192](https://cs.corp.google.com/piper///depot/google3/.nox/system-3-12/lib/python3.12/site-packages/grpc/_channel.py?l=1192): in with_call return _end_unary_response_blocking(state, call, True, None) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ state = <grpc._channel._RPCState object at 0x15204be3cce0> call = <grpc._cython.cygrpc.SegregatedCall object at 0x1520134283c0> with_call = True, deadline = None def _end_unary_response_blocking( state: _RPCState, call: cygrpc.SegregatedCall, with_call: bool, deadline: Optional[float], ) -> Union[ResponseType, Tuple[ResponseType, grpc.Call]]: if state.code is grpc.StatusCode.OK: if with_call: rendezvous = _MultiThreadedRendezvous(state, call, None, deadline) return state.response, rendezvous else: return state.response else: > raise _InactiveRpcError(state) # pytype: disable=not-instantiable E grpc._channel._InactiveRpcError: <_InactiveRpcError of RPC that terminated with: E	status = StatusCode.ALREADY_EXISTS E	details = "Could not create Cloud Run service bigframes-065f0771cfb5054c019833f3812398d3. A Cloud Run service with this name already exists. Please redeploy the function with a different name." E	debug_error_string = "UNKNOWN:Error received from peer ipv4:173.194.64.95:443 {grpc_status:6, grpc_message:"Could not create Cloud Run service bigframes-065f0771cfb5054c019833f3812398d3. A Cloud Run service with this name already exists. Please redeploy the function with a different name."}" E > [.nox/system-3-12/lib/python3.12/site-packages/grpc/_channel.py:1006](https://cs.corp.google.com/piper///depot/google3/.nox/system-3-12/lib/python3.12/site-packages/grpc/_channel.py?l=1006): _InactiveRpcError The above exception was the direct cause of the following exception: 

e2e failure:

FAILED tests/system/large/streaming/test_bigtable.py::test_streaming_df_to_bigtable FAILED tests/system/large/streaming/test_pubsub.py::test_streaming_df_to_pubsub 

These all appear unrelated. I'll rebuild the presubmit.