FnRunnerTest with non-trivial (order 1000 elements) numpy input flakes in non-cython environment

See [https://github.com/apache/beam/pull/17384#issuecomment-1117418018](https://github.com/apache/beam/pull/17384#issuecomment-1117418018)

 
```

apache_beam/runners/portability/fn_api_runner/fn_runner_test.py:141: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
apache_beam/pipeline.py:596: in __exit__
   
self.result = self.run()
apache_beam/pipeline.py:573: in run
    return self.runner.run_pipeline(self,
self._options)
apache_beam/runners/portability/fn_api_runner/fn_runner.py:200: in run_pipeline
   
pipeline.to_runner_api(default_environment=self._default_environment))
apache_beam/runners/portability/fn_api_runner/fn_runner.py:208:
in run_via_runner_api
    return self.run_stages(stage_context, stages)
apache_beam/runners/portability/fn_api_runner/fn_runner.py:409:
in run_stages
    runner_execution_context, bundle_context_manager, bundle_input)
apache_beam/runners/portability/fn_api_runner/fn_runner.py:742:
in _execute_bundle
    bundle_manager))
apache_beam/runners/portability/fn_api_runner/fn_runner.py:966:
in _run_bundle
    data_input, data_output, input_timers, expected_timer_output)
apache_beam/runners/portability/fn_api_runner/fn_runner.py:1309:
in process_bundle
    output.transform_id).append(output.data)
apache_beam/runners/portability/fn_api_runner/execution.py:242:
in append
    windowed_key_value = coder_impl.decode_from_stream(input_stream, True)
apache_beam/coders/coder_impl.py:1446:
in decode_from_stream
    value = self._value_coder.decode_from_stream(in_stream, nested)
apache_beam/coders/coder_impl.py:994:
in decode_from_stream
    c in enumerate(self._coder_impls)
apache_beam/coders/coder_impl.py:994:
in
    c in enumerate(self._coder_impls)
apache_beam/coders/coder_impl.py:617: in decode_from_stream
 
  return in_stream.read_all(nested)
apache_beam/coders/slow_stream.py:137: in read_all
    return
self.read(self.read_var_int64() if nested else self.size())
apache_beam/coders/slow_stream.py:148:
in read_var_int64
    byte = self.read_byte()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ self =  
  def read_byte(self):
      # type: () -> int
      self.pos += 1
>     return self.data[self.pos
- 1]
E     IndexError: index out of rangeapache_beam/coders/slow_stream.py:142: IndexError
```

Imported from Jira [BEAM-14410](https://issues.apache.org/jira/browse/BEAM-14410). Original Jira may contain additional context.
Reported by: bhulette.