The activitychoosertabmode setting was a legacy of the activity chooser from Moodle 4.0. However, the activity chooser has been reimplemented in 5.2, and the new layout no longer uses it.

This setting is about:

• Removing the setting
• Clear the setting on upgrade
• Remove the setting from the presets.
• Remove the javascript logic related to this setting (they have a TODO comment pointing to this issue code).