"Never send encrypted messages to unverified sessions from this session" can't be undone without restarting the client

### Steps to reproduce

1. Toggle on the global setting "Never send encrypted messages to unverified sessions from this session"
2. Type in a room to someone, who sees a "The sender has blocked you from receiving this message because your device is unverified"
3. Turn off the setting
4. Notice that the message keys are still being withheld.
5. Restart the client
6. Send a message
7. The message now comes in clearly.

### Outcome

#### What did you expect?

The messages should be received by the recipient after the setting is disabled.

#### What happened instead?

They continued to not receive messages until I restarted the client.

### Operating system

Arch Linux

### Application version

Element version: 1.11.92 Crypto version: Rust SDK 0.9.0 (5de53c7), Vodozemac 0.8.1

### How did you install the app?

Arch package

### Homeserver

half-shot.uk

### Will you send logs?

Yes

No source file or test is named. Start by reproducing the setting toggle and message-key withholding sequence in Element Web, then trace the client-side encryption state across disabling the setting and restarting. Done means messages are delivered after the setting is disabled without restarting, with a regression test covering the sequence.

Written by the indexing model from the issue text.