chore: discord invite

[Not-Sarthak]

Location (URL)

https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md

Summary

the discord invite is invalid, ideally the link should be set to 'never expire' before copying the url on server

[bjorn3]

I believe that pointed to the official discord, which has been archived. The community discord still exists though: https://discord.com/invite/rust-lang-community We should probably get rid of the link to the official discord.

[cyrgani]

A similar link exists in the std lib.rs docs:

rust/library/std/src/lib.rs

Line 97 in 9f32ccf

//! improved, submit a PR, or chat with us first on [Discord][rust-discord]