Wrong copy in Encryption settings: key storage does not store your cryptographic identity

### Steps to reproduce

1. Settings
2. Encryption
3. Look at "Key storage"
4. Read the explanatory paragraph

### Outcome

#### What did you expect?

It should explain that Key Storage is a feature meaning you can read old messages on new devices because the message keys are stored encrypted on the server.

#### What happened instead?

It incorrectly claims that Key Storage is about storing your cryptographic identity. This is not correct: Recovery is about storing your cryptographic identity, but Key Storage is only about storing message keys.

## Discussion

Earlier in our thinking, we considered "Recovery" to be part of a bigger feature called "Key storage". Since then, we have changed our minds, and now they are considered different features, with a dependency that Recovery can only be turned on if Key storage is already turned on.

There are several places in the UI and FAQ that reflect the old understanding, and need to be updated:

### In Settings - Encryption (normal view)

```
Key storage
Store your cryptographic identity and message keys securely on the server. This will allow you to view your message history on any new devices. [Learn more](https://element.io/help#encryption)
```

Should be changed to only say that key storage is about storing your message keys securely on the server. Then we should add another sentence that says something like "When key storage is turned on, Recovery may also be enabled."

### In Settings - Encryption (when turning off key storage)

```
Are you sure you want to turn off key storage and delete it?

Deleting key storage will remove your cryptographic identity and message keys from the server and turn off the following security features:
```

This should be tweaked to say that turning off key storage will also turn off Recovery.

It's also worth checking over the UI and strings for similar places that might need an update.

### In the FAQ under "What is key storage"

https://element.io/en/help#encryption5 and under "Is key storage safe?"

A similar change is needed.

Also elsewhere in the FAQ may need some tweaks.