Update README.md (#2533)

Updated the Slack link so that it doesn't break again.

README.md

@@ -4,7 +4,7 @@ chromebrew
 Package manager for Chrome OS
 
 <a href="https://join.slack.com/t/chromebrew/shared_invite/enQtNDA2MTQ5ODQ3NDc2LTA0ZmJlMGFmNmZhOTYwNDE3ZDY0NDA0MWI0OTE3MzJkYTQxN2UxMWQ1YTEzOWFmNTliMGM4NDZjYzY2NjczZGE" target="_blank"><img src="/images/slack.jpg" alt="Slack Invite" /></a>
-[Join the chat on Slack](https://join.slack.com/t/chromebrew/shared_invite/enQtMzUzMjI3NzU2NzUzLWViMGMzNzY1MDk0YTI5Y2RkMTIxMTY3OGQ0ZDYzMDRjODE0ZWI2NTM5MjBkM2Q4NGNlYzY4MGM1MzM2ZTI4NTQ)
+[Join the chat on Slack](https://join.slack.com/t/chromebrew/shared_invite/enQtNDA2MTQ5ODQ3NDc2LTA0ZmJlMGFmNmZhOTYwNDE3ZDY0NDA0MWI0OTE3MzJkYTQxN2UxMWQ1YTEzOWFmNTliMGM4NDZjYzY2NjczZGE)
 
 Supported Systems
 -----------------