Important: #104477 - Remove hyphen prefix from sys_log's data field entry 

See forge#104477

Description 

The \TYPO3\CMS\Core\Log\Writer\DatabaseWriter is used to write logs into the database table sys_log. Additional log information data is persisted in the field data and has been prefixed with a - until now. As this makes it harder to parse the data, which is JSON-encoded anyway, the prefix has been removed.

Beware that existing log entries are not migrated automatically. This leads to a mixed structure in the database table until old records are cleaned. (TYPO3 itself does not interpret the content of the field.)