context: demote "abandoned toxic match" to debug log level

[kakra]

This log message creates a overwhelmingly lot of messages in the system journal, leading to write-back flushing storms under high activity. As it is a work-around message, it is probably only useful to developers, thus demote to debug level.

This fixes latency spikes in desktop usage after adding a lot of new files, especially since systemd-journal starts to flush caches if it sees memory pressure.