Add sonic-delayed.target to Application Extension .timer file generat…

…or (#2176)

- What I did
Add sonic-delayed.target to sonic-application-extension .timer file generator
This change will complete sonic-net/sonic-buildimage#7846 of sonic-delayed.target addition.

- How I did it
N/A

- How to verify it
Make sure your App Ext is part of "WantedBy" sonic-delayed.target

sonic-utilities-data/templates/timer.unit.j2

@@ -12,4 +12,4 @@ OnBootSec=3min 30 sec
 Unit={{ manifest.service.name }}{% if multi_instance %}@%i{% endif %}.service
 
 [Install]
-WantedBy=timers.target sonic.target
+WantedBy=timers.target sonic.target sonic-delayed.target