update ticket creation button url (#22)

Author: itsMaxC

docs/setting-up/join-network.md

@@ -6,4 +6,4 @@ You are ready to join the CTRS network.  Run the following command, then open a
 sudo curl -fsSL https://pkgs.netbird.io/install.sh | sudo sh
 ```
 
-[Open a ticket](https://centrunk.atlassian.net/servicedesk/customer){ .md-button .md-button--primary }
+[Open a ticket](https://tickets.bellsys.cc/){ .md-button .md-button--primary }