Can't revoke discoverability by phone number

### Steps to reproduce

1. Go to settings > discovery
2. Click on phone number
3. Click on "revoke"

### Outcome

#### What did you expect?

My discoverability by phone number to be revoke

#### What happened instead?

The spinner spins, the revoke button is disabled, and then... the spinner dissapears, the revoke button is reverted to its enabled state... and nothing else happens

### Your phone model

_No response_

### Operating system version

_No response_

### Application version

_No response_

### Homeserver

_No response_

### Will you send logs?

Yes

Start by reproducing the failure through Settings > Discovery > phone number and inspect the revoke flow. Confirm that a successful revoke changes the discoverability state and that the spinner and button state complete normally; no source file or test is identified in the issue.

Written by the indexing model from the issue text.