UI allows (trying to) verify current session

### Description

When verifying other logins through the "User profile" screen, you can initiate a verification of the current session, which will then just fail or block indefinitely (I didn't wait) and is pointless.

### Steps to reproduce

I did not try reproducing this from scratch (in my case, I had a situation where all sessions except my new app.element.io one were already verified), but I'm assuming below would also work.

- Log in a new app.element.io session
- Go to "Security and privacy" settings.
- Note which is the current session
- Click "verify them in your User Profile" to see the session list in your profile
- Click the current session (easiest to distinguish if it's the only one that's not verified, since the current session is not highlighted, see #14344).
- Click "Verify interactively by emoji" (or something like that)
- It now tries to verify itself, waiting for itself to respond to the verification request, which will probably never happen (I waited for half a minute and then realized that this was actually the current session, so aborted and started the verification from another session).

The UI should probably not allow verification of the current session, or show a meaningful error message if you do try. In both cases, it should probably have some info on how to get the current session verified instead (this relates to #13975).

### Version information

- **Platform**: web
- **Browser**: Firefox 78
- **OS**: Ubuntu 19.10
- **URL**: https://app.element.io/