remove stability badge

the stability badge generally refers to ABI, not the production-readiness of the client

README.md

@@ -3,7 +3,6 @@
 [![Github Actions CI](https://github.com/status-im/nimbus-eth2/actions/workflows/ci.yml/badge.svg?branch=stable)](https://github.com/status-im/nimbus-eth2/actions/workflows/ci.yml?query=branch%3Astable)
 [![License: Apache](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://opensource.org/licenses/Apache-2.0)
 [![License: MIT](https://img.shields.io/badge/License-MIT-blue.svg)](https://opensource.org/licenses/MIT)
-![Stability: experimental](https://img.shields.io/badge/stability-experimental-orange.svg)
 
 [![Discord: Nimbus](https://img.shields.io/badge/discord-nimbus-orange.svg)](https://discord.gg/XRxWahP)
 [![Status: #nimbus-general](https://img.shields.io/badge/status-nimbus--general-orange.svg)](https://join.status.im/nimbus-general)