[pmon] Clean up supervisord chassis_db_init entry and fix startsecs (#10071)

Why I did it
Code review was still in progress when #9858 was merged and upon further testing I have arrived at a better solution.

How I did it
Modified supervisord configuration j2 template for pmon to require no minimum uptime for chassisd_db_init and to remove the redundant exit_codes directive

How to verify it
Boot switch and verify in syslog that there are no errors related to chassis_db_init

dockers/docker-platform-monitor/docker-pmon.supervisord.conf.j2

@@ -47,10 +47,9 @@ command=/usr/local/bin/chassis_db_init
 priority=3
 autostart=false
 autorestart=false
-exitcodes=0
 stdout_logfile=syslog
 stderr_logfile=syslog
-startsecs=10
+startsecs=0
 dependent_startup=true
 dependent_startup_wait_for=rsyslogd:running
 {% endif %}