User agreement copy does not update after changing language during account activation

[alegontarz]

Describe the bug

When a user agreement is added in another language and a new account is created, changing the language on the account activation page does not update the displayed copy. The text remains in the previously loaded language instead of switching to the selected one.

To Reproduce

Steps to reproduce the behavior:

1. Go to Edit user agreement.
2. Add a user agreement in any language. Example: Spanish.
3. Create a new account.
4. Click the activation link from the email inbox.
5. Change the language.
6. Observe that the copy does not change.

Expected behavior

After changing the language, the user agreement copy updates to the selected language.

Related work

Related to Edit CMS feature
Similar to CMS language issues found in #5339 and #5397. Not the same bugs, but may have related solutions.