[java-bigquery] Don't throw exception in BigQueryResultSet.close()

**Is your feature request related to a problem? Please describe.**
`Connection.execute*()` nethods return BigQueryResult, which contains BigQueryResultSet the inheritor of ResultSet.
Most of the methods of BigQueryResultSet are not implemented including `close()`.
Unfortunately, IntelliJ Idea strongly suggests wrapping `ResultSet` into `try-with-resources` block, which we can't do because it will trow an exception.

**Describe the solution you'd like**
Don't throw 'Not implemented' exception in the close method.

**Describe alternatives you've considered**
Fully implement `close` method to free underlying resources.

**Additional context**
IntelliJ Idea's waring: