bump debian from 12.10-slim to 12.11-slim in /postfix #148

Job	Run time
Build and push PHP 8.0	5m 48s
Build and push PHP 8.1	5m 33s
Build and push mariadb	27s
Build and push cron	28s
Build and push redis	1m 17s
Build and push nginx-proxy	29s
Build and push PHP 7.4	5m 1s
Build and push nginx	1m 51s
Build and push PHP 8.4	5m 10s
Build and push mailhog	1m 28s
Build and push PHP 8.2	5m 6s
Build and push newrelic-daemon	47s
Build and push postfix	2m 18s
Build and push PHP 8.3	4m 49s
	40m 32s

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