Deprecated function: Creation of dynamic property in PanoramaViewerFormatter::$entityTypeManager

Problem/Motivation

Right after applying the formatter to an existing image field (even without touching the options) and on every page load thereafter, I'm getting this error message:

Deprecated function: Creation of dynamic property Drupal\panorama_viewer\Plugin\Field\FieldFormatter\PanoramaViewerFormatter::$entityTypeManager is deprecated in Drupal\panorama_viewer\Plugin\Field\FieldFormatter\PanoramaViewerFormatter->__construct() (line 47 of modules/contrib/panorama_viewer/src/Plugin/Field/FieldFormatter/PanoramaViewerFormatter.php).