[Team Plans] Clarify Add Members Dialog

[svenefftinge]

We repeatedly get reports from confused users, who wanted to add members but interpreted the dialog to display the total amount of members.

Although we are moving towards a simplified design for team subscriptions, this happens often enough to be improved.

Possible Solution

I think the big "total: xxx.xx EUR" below could be one cause of confusion.
Showing the total number like:
<current> + [DROP DOWN] = <total>
could help.
@gtsiolis @jldec can you help? The solution should focus on changing the UI / messaging and be easy to implement.

[jldec]

I think all you need is wording changes