chrony: update test

Try to fix:
  2025-01-06T06:59:35Z chronyd version 4.6.1 starting (+CMDMON +NTP +REFCLOCK -RTC +PRIVDROP -SCFILTER -SIGND +ASYNCDNS +NTS +SECHASH +IPV6 -DEBUG)
  2025-01-06T06:59:35Z Disabled control of system clock
  2025-01-06T07:04:03Z No suitable source for synchronisation
  2025-01-06T07:04:03Z chronyd exiting

on some CI runs

Author: iMichka

Formula/c/chrony.rb

@@ -31,7 +31,7 @@ def install
   end
 
   test do
-    (testpath/"test.conf").write "pool pool.ntp.org iburst\n"
+    (testpath/"test.conf").write "pool pool.chrony.eu iburst\n"
     output = shell_output(sbin/"chronyd -Q -f #{testpath}/test.conf 2>&1")
     assert_match(/System clock wrong by -?\d+\.\d+ seconds \(ignored\)/, output)
   end