BigQuery: Sample is included in the wrong section of the docs

[alixhami]

The sample for creating a table shown here is the "Creating an empty table with a schema definition" section, but the sample does not have a schema specified.

To fix this:

• Move this sample to the section above: "Creating an empty table without a schema definition"
• Create a new sample with the schema specified for the "Creating an empty table with a schema definition" section