Clearing the parent from the UI using the X (or from python) clears the `parsubstr` and set `partype` back to `PAROBJECT`. Using the Clear Parent operator would leave the `parsubstr` (and thus `parent_bone`) untouched even though this operator claims to "clear parenting relationship completely" (it also removes parent deform modifiers for example). So now, also clear `parsubstr` and set back to `PAROBJECT` [which is default]. Maniphest Tasks: T88498 Differential Revision: https://developer.blender.org/D11503