Update all references from duoProAssignedUsersCount to duoAssignedUsersCount

Problem

We reference Pro in the AiMetics graphql endpoint attributes. This was because we initially only counted pro assignment which was fixed in #485506 (closed).

Solution

In #485510 (closed) we added a new attribute, duoAssignedUsersCount which we can now use instead of duoProAssignedUsersCount

Update all references from duoProAssignedUsersCount to duoAssignedUsersCount on the frontend