A selected folder assigned as a Library can be assigned to multiple Revit versions from this dialog.
Once assigned you can modify the assignment or remove the assignment to Revit version by simply reselecting the library folder and then clicking on "Assign as Library" selector once again.
NOTE: remember if the family files that you have uploaded are in a newer version that the Revit version you have shared the library to these families will not be able to be inserted. We cannot downgrade Revit family files.