docs: remove dead link to chromiumdev slack (#17161)

* docs: remove dead link to chromiumdev slack

Closes #17154

* Update chromium-development.md

docs/development/chromium-development.md

@@ -2,7 +2,6 @@
 
 > A collection of resources for learning about Chromium and tracking its development
 
-- [chromiumdev](https://chromiumdev-slack.herokuapp.com) on Slack
 - [@ChromiumDev](https://twitter.com/ChromiumDev) on Twitter
 - [@googlechrome](https://twitter.com/googlechrome) on Twitter
 - [Blog](https://blog.chromium.org)