Turning off markdown breaks sending of pills

### Steps to reproduce

When you turn off "Enable Markdown" in the options and you try to mention a users, it is no longer styled and plain text.

Mentioning users should be independant from markdown.

### Outcome

#### What did you expect?

For a mention to be correctly formatted when @ mentioning a user, even if markdown is turned off.

#### What happened instead?

The Username was displayed in plain text like "username:"

### Operating system

Ubuntu

### Browser information

Firefox 100.0.2

### URL for webapp

_No response_

### Application version

1.10.13

### Homeserver

_No response_

### Will you send logs?

No