make sure setDefaultKeyId resolves even if no change is made

[uhoreg]

fixes #5474

Make setDefaultKeyId just setAccountData and return, rather than listening for the value to come back down the sync. setAccountData already does that now, when it actually tries to change the value, and does not make an HTTP call if we try to set the account data value to the current value, which means that setDefaultKeyId would never get notified of the value being changed (since it doesn't get changed), and so would never return.

Checklist

• Tests written for new code (and old code if feasible).
• New or updated public/exported symbols have accurate TSDoc documentation.
• Linter and other CI checks pass.
• Sign-off given on the changes (see CONTRIBUTING.md).