Remove slack link in Bulgarian translation

[Roshanjossey]

🎯 Goal
Replace link to slack in 'Where to go from here' section in Bulgarian translation of Readme and put a link to code contributions like in English Readme.

💡 Possible solutions
Remove link to slack in Bulgarian translation and put a link to code contributions repo similar to main Readme.
You can find it in https://github.com/firstcontributions/first-contributions/blob/main/docs/translations/README.bg.md?plain=1#L117

Important

Please only address one issue in a PR.
Let's make it possible for more people to solve issues here.

📋 Steps to solve the problem

• Comment below about what you've started working on.
• Add, commit, push your changes.
• Submit a pull request and add this in comments - 'Addresses #'
• Ask for reviews in comments section of pull request.
• Celebrate your contribution to this project. 🎉

[gayuvick]

Hi. I would like to work on this. Is it still open?

[gayuvick]

Address #94694