Use QStringList::join(QChar) overload where applicable [QtSql]

Use QStringList::join(QChar) overload where applicable [QtSql]

This is an automated change performing the following replacements:
                    join\("(.)"\) -> join('\1')
  join\(QLatin1String\("(.)"\)\)  -> join(QLatin1Char('\1'))
  join\(QStringLiteral\("(.)"\)\) -> join(QLatin1Char('\1'))

Change-Id: Ie395d82d17710683968d006d22de313ef49dc6e5
Reviewed-by: Harald Fernengel <harald.fernengel@nokia.com>
Reviewed-by: Mark Brand <mabrand@mabrand.nl>