"Scheduled studies" is unclear label for parents

# TL;DR
The current labels for parents are "All Studies", "Studies happening right now", and "Scheduled studies" -- the label "Scheduled studies" is ambiguous between the meanings "Studies that can be scheduled" (meaning you can make an appointment) and "Studies that have been scheduled" (meaning you already have made an appointment).

# Narrative
In chatting with actual humans narrating their use of the website as part of some light UX testing, multiple people thought they would go to "scheduled studies" to see a list of appointment times they had made, once they started scheduling studies. One option could be the labels "All studies", "Studies you can do now", and "Studies you can schedule for later". Or perhaps "All studies", "Studies you can do now", and "Live studies you schedule for later"

# Acceptance Criteria
A precise description of how/when this issue will be considered closed, e.g.:

- [ ] Decide what the labels should be
- [ ] Update the site
- [ ] Update any documentation that refers to the old labels?

Start by locating the parent-facing study labels in the site and compare their current meanings with the ambiguity described in the issue. Decide on wording that distinguishes studies available now from studies that can be scheduled later, update the site, and check whether documentation refers to the old labels.

Written by the indexing model from the issue text.