update(readme): update matrix link to new room
<p align="center">
<a href="https://discord.gg/CrUAFH3"><img alt="Discord Chat" src="https://img.shields.io/discord/771367133715628073?color=%235865F2%20&label=chat%3A%20discord&style=flat-square"></a>
- <a href="https://matrix.to/#/!sYxqLOHljoSuWQiEdZ:matrix.org?via=matrix.org"><img alt="Matrix Chat" src="https://img.shields.io/matrix/zellij:matrix.org?color=%230FBD8C&label=chat%3A%20matrix&style=flat-square"></a>
+ <a href="https://matrix.to/#/#zellij_general:matrix.org"><img alt="Matrix Chat" src="https://img.shields.io/matrix/zellij_general:matrix.org?color=%230FBD8C&label=chat%3A%20matrix&style=flat-square"></a>
<a href="https://zellij.dev/documentation/"><img alt="Zellij documentation" src="https://img.shields.io/badge/zellij-documentation-fc0060?style=flat-square"></a>
</p>
