Change 'Admin and Collaborator' to 'Account owner'

[DaniBitZesty]

📝 A short description of the changes

• Change 'Admin and Collaborator' to 'Account owner'

🔗 Link to the relevant story (or stories)

• https://app.asana.com/0/1200504523179345/1207256055276973/f

Deployment implications

✅ Checklist

• Features that cannot go live are behind a feature flag/env var or specify deploy date and open PR as draft
• I have checked that commit messages make sense and explain the reasoning for each change
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have squashed any unnecessary or part-finished commits

🖼️ Screenshots (if appropriate - no PII/Prod data):

[TheDancingClown]

Do you need this line?

[DaniBitZesty]

Yess account is initialised with User.new but the association with this user doesn't work until this line. I think I could also have used
User.new(
...
account: Account.new(owner: nil),
)
Wasn't sure which was best