You can remove a teammate from your stream if they no longer need to have access to the meeting notes in it.
To do this, you will first need to make sure that your teammate is no longer on the invite of the meeting(s) for this event/series. If they are, you can edit your calendar event and choose the option "all events" when saving.
Sometimes, this will remove them from the stream for you, but if it doesn't or if they were not on the invites you can follow the steps below to remove them.
Steps:
Once you've confirmed that they're no longer an attendee on the meeting invite(s). You can click on the blue "Share" button in the upper right hand corner of the stream
Click on the "Can edit" button and pick the "Remove" option from the drop down menu
Note: If the "Can edit" button is greyed out and has a lock icon next to it, that would indicate that this teammate is still an attendee on some or all meeting invites for that stream.