Remove typo tuple-casting the query string

When running the ``get_custom_targeting_keys_by_statement`` module it raises an exception:

```
suds.WebFault: Server raised fault: '[PublisherQueryLanguageSyntaxError.UNPARSABLE @ Unable to     parse query: '('WHERE type = :type',) LIMIT 500 OFFSET 0'
Syntax error at line 1, column 1.
Extraneous input: '('.]'
```

A quick grep didn't indicate it elsewhere in the examples dir.