The journal header limits reached their maximum limit

Issue

• Annoying "Data hash table of ..." messages seen on the console.
• The system journal has a fill level of 75, which means 75% of the hash table space is being filled:

  systemd-journald[671]: Data hash table of /run/log/journal/f7d5509b13d84655ba1c31a69b407860/system.journal has a 
  fill level at 75.0(5979 of 4591616 items, 8388608 file size, 767 bytes per hash table item), suggesting rotation.
  systemd-journald[671]: /run/log/journal/f7d5509b13d84655ba1c31a69b407860/system.journal: : Journal header limits 
  reached or header out-of-date, rotating.