change invite to disc (#799)

* change invite to disc

* remove fb group

Author: pengyk

assets/email/statusEmail/Checked-in.hbs

@@ -390,11 +390,8 @@
                                                 This email is to confirm your check-in at McHacks!
                                                 <br><br>
                                                 Don't forget to join the McHacks participants <a
-                                                    href="https://facebook.com/groups/mchacks7"
-                                                    style="-webkit-text-size-adjust:100%;-ms-text-size-adjust:100%;color:#F2463A;text-decoration:none;">Facebook
-                                                    group</a> and <a
-                                                    href="https://join.slack.com/t/mchacks7/shared_invite/enQtOTA3MDc2NDU4OTAyLTI0ZWU1N2VkOGExZTA3NDg3Y2JiMGE3MGE2ZmU4MGRlYjI3YmZlYjAxYmI0OTk2ZjZjYTE0ZjNhYmY0ZDNmZmU"
-                                                    style="-webkit-text-size-adjust:100%;-ms-text-size-adjust:100%;color:#F2463A;text-decoration:none;">Slack</a>
+                                                    href="https://discord.com/invite/fqbjr43cKf"
+                                                    style="-webkit-text-size-adjust:100%;-ms-text-size-adjust:100%;color:#F2463A;text-decoration:none;">Discord</a>
                                                 for announcements, to chat with other hackers, ask questions, and form
                                                 teams!