fix: tg invite link (#9)

## 📝 Summary

<!--- A general summary of your changes -->

## 💡 Motivation and Context

<!--- (Optional) Why is this change required? What problem does it
solve? Remove this section if not applicable. -->

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## ✅ I have completed the following steps:

* [x] Run `make lint`
* [x] Run `make test`
* [ ] Added tests (if applicable)

Author: jakubhruby7

CONTRIBUTING.md

@@ -6,7 +6,7 @@ Thanks for your help improving `rbuilder`! We are so happy to have you! We just
 
 Please start by reading our [license agreement](#individual-contributor-license-agreement) below, and our [code of conduct](#code-of-conduct).
 
-The [dev Telegram](https://t.me/+csTDRpNNzAJmYTk0) is available for any questions and concerns you may have that are not covered in the documentation.
+The [dev Telegram](https://t.me/flashbots_rbuilder) is available for any questions and concerns you may have that are not covered in the documentation.
 
 If you contribute to this project, your contributions will be made to the project under both Apache 2.0 and the MIT
 license.