fix: use static discord badge instead of server id

Author: vmfunc

README.md

@@ -7,7 +7,7 @@
 [![go version](https://img.shields.io/github/go-mod/go-version/vmfunc/sif?style=flat-square&color=00ADD8)](https://go.dev/)
 [![build](https://img.shields.io/github/actions/workflow/status/vmfunc/sif/go.yml?style=flat-square)](https://github.com/vmfunc/sif/actions)
 [![license](https://img.shields.io/badge/license-BSD--3--Clause-blue?style=flat-square)](LICENSE)
-[![discord](https://img.shields.io/discord/1234567890?style=flat-square&logo=discord&logoColor=white&label=discord&color=5865F2)](https://discord.gg/sifcli)
+[![discord](https://img.shields.io/badge/discord-join-5865F2?style=flat-square&logo=discord&logoColor=white)](https://discord.gg/sifcli)
 
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