Can't copy Security Key when setting up Cross Signing

### Steps to reproduce

1. Setup Cross Signing on iOS
2. Choose Security Key
3. Tap or tap and hold on the key to attempt to copy it to the clipboard

### Outcome

#### What did you expect?
I would be able to tap or tap and hold on the Security Key to copy it to my clipboard so I could paste it in a password manager

#### What happened instead?
Nothing

Saving it to a file is... fine but not idea because then it's just sitting in plain text somewhere. I would rather put it straight in to my password manager rather than have it ever exist as plain text (likely in iCloud Drive being synced to all my other devices).

### Your phone model

_No response_

### Operating system version

iOS 15.5

### Application version

1.8.20

### Homeserver

_No response_

### Will you send logs?

No

Start by reproducing the issue in the iOS Cross Signing setup flow: choose Security Key and try tapping or holding the key. Trace the screen responsible for displaying the key and verify the completed behavior by confirming that the key can be copied directly into the clipboard without requiring a plain-text file.

Written by the indexing model from the issue text.