Updating public key from website is broken

### Steps to reproduce

1. Login on the website and load your profile (e.g. https://keybase.io/diafygi)
2. Next to your public key, click the "edit" link.
3. Two options will appear: "Update my key (I edited it elsewhere)" and "Host an encrypted copy of my private key".
4. Clicking "Update my key..." doesn't do anything. A console error says, `Uncaught TypeError: window.SigModalUis[link_data.sig_gen] is not a constructor`

### Fix

It appears this link doesn't have the appropriate data attribute that triggers the public key update flow.

To manually fix, if you inspect the link element and manually add the data field, the link works again:

Original:
```
Update my key (I edited it elsewhere)
```

Change to:
```
Update my key (I edited it elsewhere)
```

Search the website code for the link-add-signed-statement element and the data-ss_sig_gen attribute, then reproduce the profile key-edit flow in the browser. Done means the update link includes the PGPUpdate value and clicking it opens the public-key update flow without the reported constructor error.

Written by the indexing model from the issue text.