remove go-simple-db references from go-slog

- ref: https://github.com/GigaOM/legacy-pro/issues/3806
- particularly this [comment](https://github.com/GigaOM/legacy-pro/issues/3806#issuecomment-49641387)
- accompanying config: https://github.com/GigaOM/gigaom/pull/4903

[We have one](https://github.com/GigaOM/gigaom-codesniffer/blob/master/Sniffs/PHP/DeprecatedFunctionsSniff.php). We just need to update the list, I believe.