Remove deprecated "actionMenuItems"-prop in Inventory

The “actionMenItems”-prop, that can be passed to Pane and PaneHeader, has been deprecated.

Instead we have introduced the “actionMenu”-prop to replace it.

In order to fully remove “actionMenuItems” from Pane and PaneHeader in stripes-components we need to replace the prop by changing the implementation.

Procedure:
1. Remove the “actionMenuItems”-prop and any related code
2. Compose and implement an action menu and pass it to the “actionMenu”-prop